Oceans and Life — Class 9 MCQs with Answers
Class 9 CBSE Social Science · Chapter 10
72 practice questions · 24 Easy · 24 Medium · 24 Hard · Updated
Practise the most important Class 9 CBSE Social Science questions from Chapter 10, "Oceans and Life". You get 9 timed quizzes made from 72 NCERT-based MCQs, with answers and explanations. The questions are split into 24 Easy, 24 Medium and 24 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE Board exams apart.
To score well in "Oceans and Life", focus on dates, cause and effect, and reading maps and sources. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Oceans and Life, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 9 Social Science mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Oceans and Life (Class 9 Social Science)
Oceans cover most of the planet, store its heat and support an enormous range of life. This chapter covers the properties and movements of ocean water, the resources oceans provide, and how coastal communities prepare for the disasters the sea can bring.
- Extent of the oceans
- Oceans cover about 71% of the earth's surface and hold most of its water, which is why the planet looks blue from space.
- Salinity
- The quantity of dissolved salts in seawater, averaging about 35 parts per thousand and varying with evaporation, rainfall and river inflow.
- Ocean temperature
- Surface water is warmest near the equator and cools towards the poles, and temperature also falls with depth.
- Waves
- Undulations of the sea surface produced by wind; the water itself largely moves up and down while the energy travels forward.
Oceans and Life — important questions & MCQs with answers (Class 9 Social Science)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 58 are timed and scored when you sign in.
- Q1Easy
What is salinity of ocean water usually measured as?
A.Grams of salt dissolved in 1,000 grams of water✓ CorrectB.Litres of water in 1 kg of saltC.Number of waves in one hourD.Temperature of water at the surfaceAnswer: A. Grams of salt dissolved in 1,000 grams of water
Explanation: Salinity is the amount of dissolved salts, expressed as grams of salt per 1,000 grams (parts per thousand) of sea water.
- Q2Easy
The rhythmic rise and fall of sea level twice a day is called:
A.SalinityB.WavesC.CurrentsD.Tides✓ CorrectAnswer: D. Tides
Explanation: Tides are the regular rise and fall of sea water, usually occurring twice a day.
- Q3Easy
Which of the following is an important food resource obtained from the oceans?
A.WheatB.CoalC.Fish✓ CorrectD.Iron ore from mountainsAnswer: C. Fish
Explanation: Fish and other seafood are a major food resource that oceans provide to millions of people.
- Q4Easy
A series of very large ocean waves usually caused by an undersea earthquake is called a:
A.TideB.DrizzleC.CurrentD.Tsunami✓ CorrectAnswer: D. Tsunami
Explanation: A tsunami is a series of huge waves usually triggered by an earthquake under the sea floor.
- Q5Easy
Which is the most common salt that gives sea water its salty taste?
A.Potassium nitrateB.Calcium carbonateC.Magnesium sulphateD.Sodium chloride✓ CorrectAnswer: D. Sodium chloride
Explanation: Sodium chloride (common salt) is the most abundant dissolved salt in sea water and is mainly responsible for its salty taste.
- Q6Easy
Tides are mainly caused by the gravitational pull of which two bodies on the Earth?
A.The Sun and JupiterB.The Earth and MarsC.The Moon and the Sun✓ CorrectD.The Moon and VenusAnswer: C. The Moon and the Sun
Explanation: Tides are produced mainly by the gravitational pull of the Moon and, to a lesser extent, the Sun on the ocean water.
- Q7Medium
Two coastal areas have the same temperature, but one receives heavy rainfall and large amounts of river water while the other lies in a hot, dry region with little river inflow. The dry region's sea water is likely to have:
A.Higher salinity✓ CorrectB.Exactly the same salinityC.Lower salinityD.No salinity at allAnswer: A. Higher salinity
Explanation: High evaporation with little fresh water from rain or rivers concentrates the salts, so the dry region's sea water has higher salinity.
- Q8Medium
Spring tides (the highest tides) occur when:
A.There is no Moon in the skyB.The Sun and Moon pull at right angles to each otherC.The Sun, Moon and Earth are in a straight line✓ CorrectD.The sea is completely calmAnswer: C. The Sun, Moon and Earth are in a straight line
Explanation: When the Sun, Moon and Earth are aligned (new or full moon), their gravitational pulls combine to produce the highest tides, called spring tides.
- Q9Medium
Which activity is the BEST example of the blue economy working in a sustainable way?
A.Catching far more fish than can naturally replace themselvesB.Generating tidal energy while protecting marine life✓ CorrectC.Dumping factory waste into the seaD.Destroying coral reefs to build hotelsAnswer: B. Generating tidal energy while protecting marine life
Explanation: The blue economy uses ocean resources for growth without harming ecosystems; clean tidal energy that protects marine life fits this idea.
- Q10Medium
After an undersea earthquake, the safest immediate action for people on a low-lying coast is to:
A.Run towards the sea to watch the wavesB.Wait until the water has fully drained outC.Stay on the beach and collect stranded fishD.Move quickly to higher ground away from the coast✓ CorrectAnswer: D. Move quickly to higher ground away from the coast
Explanation: An undersea earthquake can trigger a tsunami, so people should move at once to higher ground away from the shore.
- Q11Medium
Why does salinity tend to be lower where large rivers like the Ganga empty into the sea?
A.Rivers raise the sea temperatureB.Rivers add salt to the seaC.Fresh river water dilutes the salt in the sea water✓ CorrectD.Rivers stop evaporation completelyAnswer: C. Fresh river water dilutes the salt in the sea water
Explanation: A large inflow of fresh river water mixes with sea water and dilutes the dissolved salts, lowering the salinity near river mouths.
- Q12Hard
Two open-ocean stations at the same latitude record different surface salinities: Station X is 32 ppt and Station Y is 37 ppt. Which single difference best explains the higher salinity at Station Y?
A.Station Y is covered by melting iceB.Station Y receives a large river and heavy monsoon rainC.Station Y lies in a hot, dry zone with strong evaporation and little fresh-water inflow✓ CorrectD.Station Y is much deeper than Station XAnswer: C. Station Y lies in a hot, dry zone with strong evaporation and little fresh-water inflow
Explanation: Strong evaporation removes water while leaving salts behind, and little fresh-water inflow means the salts are not diluted, so Station Y is saltier.
- Q13Hard
A coastal port can only handle the largest ships when the water is deepest at the harbour. The port authority should schedule such arrivals during:
A.Low tideB.High tide✓ CorrectC.A period of no wavesD.A cold currentAnswer: B. High tide
Explanation: At high tide the water at the harbour is deepest, so large, deep-draught ships can enter and leave safely; this is why ports time big arrivals with the tides.
- Q14Hard
A coastal state allows unlimited trawler fishing for quick profits. Over a few years catches fall sharply. Which conclusion best fits the blue-economy idea?
A.Regulation has no effect on fish stocksB.Fish stocks can never be harmed by humansC.More fishing always means more fish in futureD.Short-term overuse of a resource can reduce its long-term value, so use must be regulated and sustainable✓ CorrectAnswer: D. Short-term overuse of a resource can reduce its long-term value, so use must be regulated and sustainable
Explanation: Unregulated overfishing depletes stocks and lowers future catches; the blue economy stresses sustainable, regulated use so the resource lasts.
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Start this chapter free →Oceans and Life — FAQs
What are the key concepts in Class 9 Social Science Oceans and Life?+
Oceans cover most of the planet, store its heat and support an enormous range of life. This chapter covers the properties and movements of ocean water, the resources oceans provide, and how coastal communities prepare for the disasters the sea can bring. Key ideas include Extent of the oceans, Salinity, Ocean temperature, Waves.
What does Class 9 Social Science Chapter 10 (Oceans and Life) cover on XamBaaz?+
It has 72 NCERT-based MCQs on "Oceans and Life": 24 Easy, 24 Medium and 24 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE Board exams.
Are these "Oceans and Life" questions free to practise?+
Yes. Sign in with Google to practise "Oceans and Life" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Oceans and Life" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Oceans and Life" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Oceans and Life" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Oceans and Life (Class 9 Social Science)?+
The questions that matter most test Extent of the oceans, Salinity, Ocean temperature, Waves. This page shows 14 solved important MCQs with answers and explanations; all 72 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Oceans and Life?+
Yes — Class 9 Social Science Oceans and Life has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.