The atmosphere of Venus is quite different from ours. Measurements taken from the Earth show a high concentration of carton dioxide in the atmosphere of Venus. In fact, carbon dioxide makes up 96 percent of Venus* atmosphere; nitrogen makes up almost all the rest. The Earth's atmosphere, by comparison, is mainly nitrogen, with a fair amount of oxygen as well. Carbon dioxide makes up less than 0.1 percent of the terrestrial atmosphere, The surface pressure of Venus* atmosphere is 90 limes higher than the pressure of Earth's atmosphere, as a result of the large amount of carbon dioxide in the former.
Throughout Earth's history, carbon dioxide on Earth has mixed with rain to dissolve rocks; the dissolved rock and carbon dioxide eventually flow into the oceans, where they precipitate to fonn new terrestrial rocks, often with the help of life-forms. If this carbon dioside were released from the Earth's rocks, along with ower carton dioxide trapped in seawater, our atmosphere would become as dense and have as high a preasore as that of Venus. Venus, slightly closer to the Sun than Earth and thus hotter, had no'oceans in which the carbon dioxide could dissolve or life to help take up the carbon. Also, Venus has probably lost almost all the water it ever had. Since Venus is closer to the Sun than the Earth is, its lower atmosphere was hotter even early on. The result was that more water vapor went into its upper atmosphere, where solar ultraviolet rays broke in up into hydrogen and oxygen. The hydrogen, a light gas, escaped easily; the oxygen has combined with other gasses or with iron on Venus1 surface.
Studies from the Earth show that the clouds on Venus are primarily composed of droplets of sulfuric acid, with water droplets mixed in* Sulfuric acid may sound strange as a cloud constituent, but the Earth too has a significant layer of sulfuric acid droplets in its stratosphere. However, the water in the lower layers of the Earth's atmosphere, circulating because of weather, washes the sulfur compounds out of these layers, whereas Venus has sulfur compounds in me lower layers of its atmosphere in addition to those in its clouds.
1. What does the passage mainly discuss?
(A) Atmospheric differences between Venus and Earth
(B) How Venus lost the water it once had
(C) The influence of the Sun on Venus
(D) A comparison between the upper and lower atmosphere on Venus
2. The phrase “the former” refers to
(A) the surface pressure
(B) Venus1 atmosphere
(C) Earth's atmosphere
(D) a result
3. The word "eventually" is closest in meaning to
(A) in the past
(B) first
(C) ultimately
(D) occasionally
4. According to the passage, what causes Venus' high surface pressure?
(A) Dissolving rocks
(B) Frequent heavy rains
(C) Its distance from the Sun
(D) The composition of its atmosphere
5. Why does the author begin the sentence with the phrase "If this carbon dioxide were released from Earth's rocks,.-."'
(A) To present a situation that is contrary to fact
(B) To convince readers that a certain process is harmless
(C) To describe an event that took place long ago
(D) To explain what is likely to happen in the future
6. The word "trapped" is closest in meaning to
(A) caught
(B) transported
(C) lacking
(D) involved
7. According to the passage, which of the following has resulted from processes involving Earth’s carbon dioxide?
(A) A steady increase in the density of Earth’s atmosphere
(B) An increased rate at which rock dissolves
(C) The accumulation of carbon dioxide in Earth’s rocks
(D) The expansion of Earth’s oceans
8. The passage suggests that which of the following helps explain; why Earth has kept most of its water?
(A) Earth's surface contains only small amounts of iron.
(B) Earth has always been cooler than Venus.
(C) Earth now has higher amounts of carbon dioxide than it used to have.
(D) Earth's atmosphere has never completely blocked sulfuric acid droplets,
9. Avoiding to the passage, what happened to oxygen on Venus'?
(A) Most of it was absorbed into rocks.
(B) It was released from water and then combined with other substances.
(C) It chemically combined with hydrogen to form atmospheric water,
(D) It has been slowly replacing carbon dioxide in Venus' upper atmosphere,
10. The word "constituent” is closest in meaning to
(A) type
(B) alternative
(C) product
(D) component
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