The rhythmic rise and fall of ocean water twice in a day is called ______.

The correct answer is B, Gerusoppa. The Sharavati river in Karnataka falls from a height of about 253 metres as Jog Falls, which is also called Gerusoppa Falls after the village nearby, and Jogada Gundi in the local tongue. It is among the highest plunge waterfalls in India, and the water comes down in four separate streams named Raja, Rani, Roarer and Rocket. The Linganamakki dam upstream now controls the flow, so the falls are at their finest during the monsoon. Option A is wrong because Hogenakkal is on the Kaveri in Tamil Nadu, close to the Karnataka border. Option C is wrong because Soochipara, or Sentinel Rock falls, is on the Chaliyar in Wayanad, Kerala. Option D is wrong because Athirappilly is on the Chalakudy river in Kerala and is called the Niagara of India. Exam tip: the Sharavati makes Jog or Gerusoppa Falls in Karnataka, while the Kaveri makes Hogenakkal and Shivanasamudra.

The correct answer is C, 15. The Planning Commission divided India into 15 agro-climatic zones in 1989, so that farm planning could follow soil, climate, rainfall and water resources rather than State boundaries. The zones run from the Western Himalayan Region and the Trans-Gangetic Plains to the East Coast Plains and Hills, the Western Dry Region and the Islands Region. The idea was to match crops and cropping patterns to the land, and it is still the base on which farm research and extension work are planned. Option A is wrong because 20 is not the Planning Commission's figure. Option B is wrong because 10 is too few and matches no such classification. Option D is wrong because 30 confuses this division with the far larger number of agro-climatic sub-zones worked out by the ICAR. Exam tip: the Planning Commission marked 15 agro-climatic zones in 1989, while the ICAR uses 127 agro-climatic sub-zones.

The correct answer is C, The air always moves from high pressure areas to low pressure areas. Air flows from where pressure is high to where it is low, and that moving air is what we call wind; the greater the difference in pressure, the stronger the wind. The Coriolis force then bends this flow, to the right in the Northern Hemisphere and to the left in the Southern. Option A is wrong because high pressure means sinking air, which brings clear skies and dry weather. Option B is wrong because low pressure means rising air that cools and condenses, so it brings clouds and rain. Option D is wrong because air pressure is highest at sea level, about 1,013 millibars, and falls as one goes up and the air thins. Pressure is measured with a barometer and shown on weather maps by isobars, the lines joining places of equal pressure. Exam tip: high pressure means sinking air and clear weather; low pressure means rising air, clouds and rain.

The correct answer is D, Sikkim. Sikkim does not touch Myanmar. Its neighbours across the border are Nepal to the west, China in the north and east, and Bhutan to the south-east. Only four Indian states share the border with Myanmar - Arunachal Pradesh, Nagaland, Manipur and Mizoram - and that border runs for about 1,643 km. Option A is wrong because Arunachal Pradesh meets Myanmar along its south-eastern edge. Option B is wrong because Mizoram has a long stretch of the Myanmar border besides its border with Bangladesh. Option C is wrong because Manipur meets Myanmar on the east, and Moreh in Manipur is the main trading town on that border. Sikkim is India's least populated state and shares borders with three countries, but Myanmar is not one of them. Exam tip: remember the Myanmar border states as A-N-M-M - Arunachal Pradesh, Nagaland, Manipur and Mizoram.

The correct answer is B, Sandstone. Sandstone is a sedimentary rock: grains of sand carried by rivers or wind settle in layers and harden over time. Metamorphic rocks are different, being older rocks changed in place by great heat and pressure inside the crust, which is why they are harder and often banded. Option A is wrong because marble is limestone that has been metamorphosed. Option C is wrong because quartzite is the metamorphic form of sandstone itself. Option D is wrong because slate is metamorphosed shale and splits into thin sheets. Rocks fall into three families: igneous, formed from cooling magma or lava, sedimentary, formed from deposits, and metamorphic, formed by change. They pass from one family to another through the rock cycle, so sandstone can turn into quartzite, and any rock that melts and cools again becomes igneous. Exam tip: limestone becomes marble, sandstone becomes quartzite, shale becomes slate and coal becomes graphite.