In order for one to achieve (A) the desired (B) results in this experiment, it is necessary that he works (C) as fast as possible (D).
答案是(C),work才对。
为什么呢?that后面加完整的句子,那么works怎么会不对呢?
我猜想:是不是因为那个位置应该是 should work 而should省略,才会留下work?
Biologists tell us that the earth has seen 500 milliion spescies and animals ___ or so.
(A) During the last 3 billion years
(D) Since the last 3 billion years
两个感觉很相似,也跟has been很符合。
但是老师说since 后面要加ago才对,WHY?
第一题你说的正确。
第二题,during 是指在过去的。。。年间。since是自从。since 只能接一个时间点,不能带时间段。有since前面多数是完成时。
Since the last 3 billion years是指就在 3 billion years 前的那一天has seen 500 milliion spescies and animals
since....ago表示“自 3 billion years 前的那一天开始(到现在)”意思就和during 差不多了
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