托福阅读真题+题目+答案：Where Life Arose

托福阅读真题+题目+答案：Where Life Arose

Life could not have come into being on Earth until after about 4 billion years ago, when bombardment by asteroids had subsided substantially. ▋Even after Earth's surface had stabilized, certain conditions were required for the origin of life.▋ Some researchers have concluded that precursor compounds, and ultimately life itself, arose small bodies of water that were struck by lightning and turned into what is sometimes referred to as the "primordial soup" of organic compounds.▋ The problem with that idea is that it would have required an atmosphere lacking oxygen, because even a small amount of oxygen would have oxidized, and thereby destroyed, chemical raw materials necessary for the production of essential organic compounds.▋

1According to paragraph 1, researchers who believe that life began in small bodies of water on Earth's surface also believe that

A.precursor compounds were formed when asteroids struck Earth's surface

B.Earth's atmosphere contained no oxygen when the first organic compounds formed

C.bombardment by asteroids increased after Earth's surface stabilized

D.lightning delayed the formation of organic compounds

Knowing that photosynthesis produces the preponderance of oxygen in Earth's atmosphere today, scientists once assumed that the atmosphere lacked free oxygen before the origin of photosynthetic organisms. We now know, however, that ultraviolet light breaks down water vapor in Earth's upper atmosphere, slowly liberating oxygen which spreads in small quantities throughout the atmosphere. This process would have contributed a small amount of oxygen to the ancient atmosphere-enough to destroy chemical compounds essential to life. Life must have originated not in a small body of water that was exposed to atmospheric oxygen but in some environment that was isolated from Earth's atmosphere. The most likely setting was a warm area beneath the seafloor in the vicinity of a mid-ocean ridge (submarine mountain range).
2.In paragraph 2, why does the author discuss the fact that ultraviolet light produces oxygen from water vapor in the atmosphere?

A.To explain why scientists no longer believe that the first organisms used photosynthesis.

B.To explain the earliest possible date for the formation of life.

C.To refute the view that life originated in small bodies of water.

D..To explain why there was little water vapor water in Earth's early atmosphere

3.The word “isolated” in the passage is closest in meaning to

A.derived

B.separated

C.condensed

D.eliminated

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