The (i)________of molecular oxygen on Earth-sized planets around other stars in the universe would not be (ii)________sign of li

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问题 The (i)________of molecular oxygen on Earth-sized planets around other stars in the universe would not be (ii)________sign of life: molecular oxygen can be a signature of photosynthesis (a biotic process) or merely of the rapid escape of water from the upper reaches of a planetary atmosphere (an abiotic process).
Blank (i)      Blank (ii)
A. dearth      D. a controversial
B. presumption E. an unambiguous
C. detection   F. a possible

选项

答案C,E

解析 逻辑连接标志是冒号,表示对于前面内容的解释。冒号前面说宇宙中环绕其他恒星的类地行星上氧分子的(i)________将不是(ii)________生命迹象。冒号后面解释说,氧分子可以是光合作用(一个生物过程)的标志或者仅仅是水从行星上层大气中快速逃逸的标志(非生物过程)。既然非生物过程也能产生氧,所以氧的存在不一定是生命存在的确切证据,所以空格(i)填入表示氧分子存在的词,选C项detection(发现)。空格(ii)填表示“确切的”含义的词,选E项all unambiguous(确凿的)。
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