GWD-6-Q31(prep08-2-220)

默默楚

GWD6-Q31:
The fact of some fraternal twins resembling each other greatly and others looking quite dissimilar highlights an interesting and often overlooked feature of fraternal-twin pairs, namely they vary considerably on a spectrum of genetic relatedness.



A.The fact of some fraternal twins resembling each other greatly and others looking quite dissimilar highlights an interesting and often overlooked feature of fraternal-twin pairs, namely they vary considerably

B.That some fraternal twins resemble each other greatly while others look quite dissimilar highlights an interesting and often overlooked feature of fraternal-twin pairs, namely that they vary considerably

C.With some fraternal twins resembling each other greatly and others looking quite dissimilar, it highlights an interesting and often overlooked feature of fraternal-twin pairs, namely considerable variation

D.With some fraternal twins resembling each other greatly and others looking quite dissimilar, it is a fact that highlights an interesting and often overlooked feature of fraternal-twin pairs, namely a considerable variation

E.Because some fraternal twins resemble each other greatly and others look quite dissimilar, this fact highlights an interesting and often overlooked feature of fraternal-twin pairs, namely they vary considerably

Prep对namely解释了三种用法：
（1）补充说明前面离他最近的名词成分
（2）补充说明句子的主语
（3）namely后面跟从句解释前面的名词成分
并且对此题中namely解释是用法（2）

这题的namely后面不是跟从句么？ 怎么补充说明句子的主语了。。。

还有namely that they vary considerably on a spectrum of genetic rwlatedness 中的they指谁呢？