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  3. One way to determine which planets outside the solar system might harbor lif

One way to determine which planets outside the solar system might harbor lif

游客2025-02-19  14
问题     One way to determine which planets outside the solar system might harbor life is to look for telltale signs in their light. Living organisms create a chemical disequilibrium in their environment, typically indicated by a molecule whose presence can be explained only if some presence is continually regenerating it. For example, Earth’s atmosphere contains oxygen because photosynthesis produces it faster than it is lost through processes such as the rusting of iron in rocks. However, chemical disequilibrium does not necessarily indicate the presence of life because, as in the case of methane on Mars, the imbalance could arise through nonbiological processes. [br] The passage mentions that “Earth’s atmosphere contains oxygen” primarily in order to
选项 A、contribute to a discussion of the nature of photosynthesis
B、give an example of a chemical disequilibrium
C、identify an element that scientists are looking for on Mars
D、illustrate a process that occurs only on Earth
E、introduce a contrast between oxygen and methane Consider each of the choices separately and select all that apply.
答案 B
解析 本题属于目的题，定位句是第三句，很明显是例子，用来介绍前文捉及的化学失衡，所以选项B正确。
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