GWD17-Q32

bolococo

32. GWD17-Q32:

Navigatorshave known for thousands of years that the ocean has variable currents, but itis only in the last half century that a reasonably clear picture has emergedof the patterns and causes of ocean currents.

A    a reasonably clear picture has emerged of the     patterns and causes of ocean currents
B   a reasonably clear picture of the patterns of ocean     currents and their causes have emerged
C   a reasonably clear picture emerged of ocean     currents, their patterns and the causes of them
D   there have emerged a reasonably clear picture of     the patterns of ocean currents and what caused them
E     there had emerged areasonably clear picture of the patterns of ocean currents and their causes

能解释一下这题为什么A正确么？in the last half century不是一个确定的时间点嘛，为什么可以用完成时？

sunflower88

if 不能引导表语从句，排除A/B

C中的they, 指代有歧义

比较D/E， 两个whether引导的从句中，结构对称 chimpanzees -- other animals, 选E

hazardous

加the 和不加the 是不一样的哈
e.g. : Did you see the game on TV last night? 昨天晚上
e.g. : Interest in golf has grown rapidly in the last ten years. 最近十年

bolococo

噢~~！！！原来如此！！！谢谢啦~