Graves drew two conclusions from these observations. First, at least some of the observed differences between the enzymes of the Atlantic and Pacific fish
populations were not random but were the result of evolutionary adaptation. Second, it appears that closely related populations of fishes on both sides of the isthmus are starting to genetically diverge from each other. Because Graves’s study of geographically isolated populations of isthmus fishes offers a glimpse of the beginning of a process of gradual accumulation of mutations that are neutral or adaptive, divergences here might be evidence of allopatric speciation in process. Q12 Which of the sentence below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
A. Graves’s study provides evidence that isthmus fishes are in the process of becoming geographically isolated.
B. Graves’s study of mutating isthmus fishes yields results that differ from results of other studies involving allopatric speciation.
C. Graves’s study of isolated populations of isthmus fishes provides some evidence that allopatric speciation might be beginning.
D. Graves’s study indicates that when isolated, populations of isthmus fishes register neutral or adaptive mutations.
1. 首先确定句子核心信息
Because Graves’s study of geographically isolated populations of isthmus fishes offers a glimpse of the beginning of a process of gradual accumulation of mutations that are neutral or adaptive, 【divergences here might be evidence of allopatric speciation in process.】
词汇：
A glimpse of 看见，瞥见 Mutation 突变，变种
Divergence 变化，变异
Allopatric speciation 异地物种形成
2. 理解大意
该句是由because引导的原因状语从句和方括号内的主句组成的嵌套句，从句的主谓宾已用绿色字体标出，大意为：因为G的研究让人们看到了突变的逐渐累积过程的开始，所以这里的变异可能是正在进行中的异地物种形成的证据。也即是说：G的研究为异地物种形成提供了证据。
3. 核对选项
A. Graves’s study provides evidence that isthmus fishes are in the process of
becoming geographically isolated.
A选项主句信息缺失
B. Graves’s study of mutating isthmus fishes yields results that differ from results of
other studies involving allopatric speciation. B选项提到“不同”，而原句未提及
C. Graves’s study of isolated populations of isthmus fishes provides some evidence
that allopatric speciation might be beginning.
C选项说到G关于鱼的研究为异地物种形成的开始提供了证据，与之前分析的大意一致
D. Graves’s study indicates that when isolated, populations of isthmus fishes
register neutral or adaptive mutations. D选项主句信息缺失
所以该题正确答案为C。
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