求助 救救这个可怜的孩子吧！prep九套第一套 p2-sc 8. (24773-!-item-!-188;#058&001691)

heart0120

Q20p2-sc 8.(24773-!-item-!-188;#058&001691)



Ozone, a special form of oxygen that screens out harmful ultraviolet rays, reaches high concentrations twelve miles above Earth, where it has long appeared that it was immune from human influence; we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer.



(A) has long appeared that it was immune from

(B) has long appeared to have been immune from

(C) has long appeared as being immune to

(D) had long appeared immune to

(E) had long appeared that it was immune to

答案是D，请问为什么用过去完成时呢？没发现过去的时间提示啊！！！

Lacus

（臭氧）以前（=had）是不受人类影响的，如今我们已经意识到氟氯碳化物破坏臭氧。

注意分号后是一个转折。

heart0120

可是，表示与现在对比，用一般过去时就好了。。。过去完成应当表示过去的过去啊。。。
在一个没有任何时间状语，且没有任何过去动作先后性暗示的句子中，用一个过去完成时，不是很别扭吗？

heart0120

自己顶！！时态这方面很不好的说，自己是学法语的，跟英语有点混，
希望大侠们飘过，拯救一下我吧，最好能详细说说。。。
先谢过！！！这厢有礼了！！！

Lacus

abc（it has）的时态和we have realized...一句的时态是相同的，所以要表示臭氧在“我们认识到”以前是不受人类影响的，只能更“早”的had咯。

heart0120

恩。。。明白了。。。
但是说如果有过去一般时的选项，也是可以的呢。。。