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An organism X having breathing organs A lives on land. When organism X goes under water, it cannot survive for a long time unless carrying an oxygen cylinder. On the other hand, the organism Y having breathing organs B always lives in water and if taken out of water, it dies after a short while. A third organism Z having breathing orgains C and D which lives on the banks of ponds, lakes and rivers can survive on land as well as in water equally well. (a) What could organism X be? Name the breathing organs A. (b) What could organism Y be? Name the breathing orgains B. (c) What could organism Z be ? Name the breathing organs C and D (d) Out of X, Y and Z, which organism is (i) amphibian, (ii) aquatic, and (iii) terrestrial ?

Read the passage carefully and select the best answer to each question out of the given four alternatives. The Amazon basin has been continuously inhabited for at least 10, 000 years, possibly more. Its earliest inhabitants were stone-age peoples, living in hundreds of far-flung tribes, some tiny, others numbering in the tens of thousands. It was from the west that Europeans explorers first arrived. In 1541 a Spanish expedition from Quito, led by Gonzalo Pizarro, ran short of supplies while exploring east of the Andes in what is today Peru. Pizarro’s cousin Francisco de Orellana offered to take 60 men along with the boats from the expedition and forage for supplies. De Orellana floated down the Rio Napo to its confluence with the Amazon near Iquitos (Peru), and then to the mouth of the Amazon. Along the way his expedition suffered numerous attacks by Indians, some of the Indian warriors, they reported, were female, like the Amazons of Greek mythology, and thus the world’s greatest river got its name. No one made a serious effort to claim this sweat territory, however, until the Portuguese built a fort near the mouth of the river at Belém in 1616, and sent Pedro Teixeira up the river to Quito and back between 1637 and 1639. During the 17th and 18th centuries, Portuguese bandeirantes (groups of roaming adventurers) penetrated ever further into the rain forest in pursuit of gold and Indian slaves, exploring as far as present-day Rondônia, and the Guaporé and Madeira river valleys. Amazonian Indians had long used the sap from rubber trees to make waterproof bags and other items. European explorers recognized the potential value of natural latex, but were unable to market it because it tended to grow soft in the heat, or brittle in the cold, and thus had limited appeal outside the rain forest. However, in 1842 American Charles Goodyear developed vulcanization (made natural rubber durable) and in 1890 Ireland’s John Dunlop patented pneumatic rubber tires. Soon there was an unquenchable demand for rubber in the recently industrialized USA and Europe, and the price of rubber on international markets soared. As profits skyrocketed, so did exploitation of the seringueiros, or rubber tappers, who were lured into the Amazon, mostly from the drought-stricken northeast, by the promise of prosperity only to be locked into a cruel system of virtual slavery dominated by seringalistas (owners of rubber-bearing forests). Rigged scales, hired guns, widespread illiteracy among the rubber tappers, and monopoly of sales and purchases all combined to perpetuate the workers’ debt and misery. In addition, seringueiros had to contend with jungle fevers Indian attacks and all manner of deprivation. Where did De Orellano float down to for its confluence with the Amazon?

A voltage applied to an X -ray tube being increased eta = 1.5 times, the short-wave limit of an X -ray continuous spectrum shifts by Delta lambda = 26 pm . Find the initial voltage applied to the tube.

Answer the following questions: (a) Long distance radio broadcasts use short-wave bands. Why? (b) It is necessary to use satellites for long distance TV transmission. Why? (c) Optical and radiotelescopes are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth. Why? (d) The small ozone layer on top of the stratosphere is crucial for human survival. Why? (e) If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now? (f) Some scientists have predicted that a global nuclear war on the earth would be followed by a severe ‘nuclear winter’ with a devastating effect on life on earth. What might be the basis of this prediction? Answer the following questions: (a) Long distance radio broadcasts use short-wave bands. Why? (b) It is necessary to use satellites for long distance TV transmission. Why? (c) Optical and radiotelescopes are built on the ground but X-ray astronomy is possible only from satellites orbiting the earth. Why? (d) The small ozone layer on top of the stratosphere is crucial for human survival. Why? (e) If the earth did not have an atmosphere, would its average surface temperature be higher or lower than what it is now? (f) Some scientists have predicted that a global nuclear war on the earth would be followed by a severe ‘nuclear winter’ with a devastating effect on life on earth. What might be the basis of this prediction?

The voltage applied to the Coolidge X-ray tube is increased by 25%. As a result the short wave limit of continuous X-ray spectrum shifts by Delta lambda . The initial voltage applied to the tube is