Which one of the following statements is correct with reference to normal lapse rate?

The correct answer is C, Reduction in the vegetation cover to arrest landslide. Cutting the vegetation on a slope makes landslides more likely, not less, so it can never be a mitigation measure. Roots bind the soil and hold a slope together, and the leaf cover breaks the force of falling rain; where the forest is cleared, the loose soil slides down with the first heavy spell. The measures actually used are hazard zonation and mapping, retaining walls and benching of slopes, control of surface and subsurface drainage, afforestation on the slope, and limits on construction and blasting in fragile hill areas. A is wrong because a retaining wall holds the slipping mass in place and is a standard engineering step. B is wrong because hazard mapping marks the vulnerable belts so that building can be kept away from them. D is wrong because leading rainwater and spring flow away removes the water pressure that sets a slide off. Exam tip: afforestation helps and deforestation hurts; in India the Himalayas and the Western Ghats are the most landslide-prone regions.

The correct answer is A, Horizontal equal halves. The equator is the latitude of 0 degrees and it runs east to west round the middle of the earth, cutting the globe into two equal halves. These halves are the Northern Hemisphere and the Southern Hemisphere, and each stretches through 90 degrees of latitude up to its pole. The equator is the longest parallel, about 40,075 km round the earth, and every other parallel is shorter than it. Day and night stay nearly equal through the year on the equator, and the sun is overhead there on the two equinoxes, 21 March and 23 September. B is wrong because the equator is not drawn at a slant; it lies at right angles to the earth's axis. C is wrong because the two parts it makes are equal, not unequal. D is wrong because the vertical division is made by the Prime Meridian, which marks off the Eastern and Western Hemispheres. Exam tip: the equator divides north from south, the Prime Meridian divides east from west.

The correct answer is A, Uttar Pradesh. Uttar Pradesh grows more wheat than any other state, because the fertile alluvial soil of the Ganga plain, canal and tubewell irrigation and a cool winter together suit the crop. Wheat is India's chief rabi crop: it is sown between October and December and harvested in March and April, and it needs a cool growing season with a warm, dry spell for ripening. Uttar Pradesh is followed by Madhya Pradesh and Punjab in total output, while Punjab and Haryana lead in yield per hectare because their irrigation is assured. B is wrong because Punjab, though the backbone of the central grain pool, has a far smaller cropped area than Uttar Pradesh. C is wrong because Haryana is a small state and its total output stays well below both. D is wrong because Madhya Pradesh has climbed to second place but still trails Uttar Pradesh. Exam tip: Uttar Pradesh leads in total wheat production, Punjab in productivity per hectare.

The correct answer is B, Halocline. The halocline is the layer in a vertical section of the ocean in which salinity changes sharply with depth; the name comes from the Greek halos, meaning salt. It usually lies within the upper few hundred metres, between the well mixed surface water and the far more uniform deep water, and it is sharpest where fresh water from rivers, heavy rain or melting ice floats above saltier water, as in the Bay of Bengal and the polar seas. Option A is wrong because the thermocline is the layer where temperature falls quickly with depth. Option C is wrong because the photic or euphotic zone is the sunlit upper layer in which photosynthesis is possible, which is a matter of light and not of salt. Option D is wrong because the pycnocline is the layer of rapid change in density, which results from the temperature and salinity changes together. Exam tip: thermo for heat, halo for salt and pycno for density.

The correct answer is B, 2, because the first two statements are right and the third is wrong. An anticyclone is a system of high pressure, with the highest pressure at its centre, and the air there sinks from above. As it sinks it is compressed and warms, so clouds cannot form and the weather stays clear, calm and dry; winter fog and summer heat waves both settle in under anticyclones. The winds of an anticyclone diverge, blowing outward from the centre, clockwise in the northern hemisphere and anticlockwise in the southern, so statement three is false: converging winds belong to a cyclone, where air rises and brings cloud and rain. Option A is wrong because two statements, not one, are correct. Option C is wrong because it counts the false third statement as well. Option D is wrong because two statements do hold. Exam tip: anticyclone means high pressure, sinking air, diverging winds and fair weather, the mirror image of a cyclone.