我来回答这个问题吧,
z8_cn 说得不错,has 是现在完成时,表示一直延续到现在的动作. had是过去完成时,表示一直延续到过去某个时间点的动作.Had完成时一般要与表时间的状语连用.比如.
He had been waiting there for 3 hours when I got to the airport yesterday.
当我昨天赶到机场的时候,他已经在那里等了3小时了.等这个动作一直延续到我昨天去机场这个时间点,所以用过去完成时,这里有时间状语when I got to the airport yesterday.
在机场见面的当时,他可以这么说
Why do you come so late? I have been waiting here for 3 hours!
因为就他说话的时候,等的动作是延续到现在的.用现在完成时.
kingofhill举的第二个例子不是很完整,如果有上下文或在一个对话的环境中才可以这么说,过去完成时一般不会脱离时间状语而独立出现
--- What did you do when you were in US? (这时你已经回国了)
--- I had been learning English for five years. (这里后面其实省略了before I came back to China, 在我回国之前,我在那里学了5年英语.现在有可能还在学也有可能没学了,但这个不重要,不是他们讨论的重点)
回到你问的这个句子,这里If Newton lived today 是一个虚拟条件从句,对后面主句的时间段没影响
he would be surprised by what___ in science and technology 这个句子中,主语是what has discovered in science and technology, 这里的discover是延续到今的,至今为止所发现的科学技术
如果要用had discovered, 要这么说:
If Newton lived today, he would be surprised by what had discovered in science and technology before 21st century.
如果牛顿住还在世的话,他会为被21世纪前所发掘的科学和技术感到惊讶.
这里就是过去的一个时间点(2000年1月1日)之前的动作的延续.
希望你明白了
If Newton lived today,he would be surprised by what _____
If Newton lived today,he would be surprised by what _____
If Newton lived today,he would be surprised by what___ in science and technology.
答案是has been discovered ,为什么不是had been discovered.
If Newton lived today,he would be surprised by what___ in science and technology.
答案是has been discovered ,为什么不是had been discovered.
英语人气:460 ℃时间:2019-11-15 07:11:36
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