Over the past century, the composition of the human gene pool ______ appreciably.

admin2015-03-26 23

问题 Over the past century, the composition of the human gene pool ______ appreciably.

选项 A、did not change
B、has not changed
C、was not changed
D、had not changed

答案B

解析时态题。在含有since，so far，as yet(to date)，over(in)the past．．．等短语作状语的句子中，谓语动词常用现在完成时，故B正确。

转载请注明原文地址:https://www.kaotiyun.com/show/vcHK777K

专业英语四级

相关试题推荐

随机试题

最新回复(0)