The Challenger Deep, the deepest known point of the world's oceans, lies in which trench?

The correct answer is B. By area the order of the continents is Asia, about 44 million square kilometres, then Africa with about 30 million, North America with about 24 million, South America with about 18 million, Antarctica with about 14 million, Europe with about 10 million and Australia with about 8 million. Option A is wrong because it places South America above North America, which is a common slip since South America is longer but narrower. Option C is wrong because Africa is the second largest continent, not the first; Asia alone covers nearly a third of the land surface. Option D is wrong because North America is smaller than Africa. A simple memory aid for the order is the sentence pattern Asia, Africa, North, South, Antarctica, Europe, Australia, which also happens to run from the most populous to the least.

The correct answer is C, Pacific Ocean. It is the largest ocean, covering nearly half the total ocean surface, and the deepest, because the Challenger Deep in its Mariana Trench is the deepest known point on earth; its rim of volcanoes and earthquake zones is called the Ring of Fire. Option A is wrong because the Atlantic is the second largest, known for its S shape, its Mid-Atlantic Ridge and the busiest shipping routes. Option B is wrong because the Indian Ocean ranks third and is the only ocean named after a country. Option D is wrong because the Arctic is the smallest and shallowest ocean, largely covered with drifting sea ice. Note the pairing examiners use: largest and deepest go together in the Pacific, while smallest and shallowest go together in the Arctic.

The correct answer is C, Indian Ocean. It takes its name from India, whose peninsula projects into it, and this is the only case of an ocean named after a nation; it is also unusual in being closed in the north by the Asian landmass, which makes its monsoon-driven currents reverse twice a year. Option A is wrong because the Arctic Ocean is named from the Greek word for the bear, through the constellation that marks the north. Option B is wrong because the Southern Ocean is named for its position around Antarctica and was recognised as a separate ocean only in 2000. Option D is wrong because the Atlantic takes its name from Atlas of Greek mythology and from the Atlas Mountains of north-west Africa. Remember that the Indian Ocean is also the warmest of the oceans and the third largest by area.

The correct answer is C, 2000. In that year the International Hydrographic Organization recognised the waters surrounding Antarctica, broadly south of sixty degrees south latitude, as the fifth ocean of the world, which is why older textbooks speak of four oceans and newer ones of five. Option A is wrong because 1982 is the year of the United Nations Convention on the Law of the Sea, an agreement about maritime zones rather than about naming an ocean. Option B is wrong because 1992 is remembered for the Earth Summit at Rio de Janeiro. Option D is wrong because no ocean was recognised in 2010. The Southern Ocean carries the Antarctic Circumpolar Current, the only current that flows right around the globe, and it is the stormiest stretch of water on earth.

The correct answer is B, Africa. Africa is the only continent through which all four of these lines pass: the Equator crosses its middle, the Tropic of Cancer runs across the Sahara, the Tropic of Capricorn crosses its southern part, and the Prime Meridian passes through its western bulge near Accra. Option A is wrong because the Tropic of Capricorn lies entirely south of Asia and the Prime Meridian does not touch it. Option C is wrong because South America is crossed by the Equator and the Tropic of Capricorn but not by the Tropic of Cancer or the Prime Meridian. Option D is wrong because Australia is crossed only by the Tropic of Capricorn, since it lies wholly in the Southern Hemisphere. This single fact makes Africa the most symmetrical of the continents about the Equator.