GWD26-Q20与pp-2-08中时态选择的矛盾求教

 GWD26-Q20

In 1981 children in the United States spent an average
        of slightly less than two and a half hours a week doing
        household chores; by 1997 they had spent nearly six hours a week.

A.      chores; by 1997 they had spent nearly six hours
        a week

B.       chores; by 1997 that figure had grown to nearly
        six hours a week

C.      chores, whereas nearly six hours a week were
        spent in 1997

D.      chores, compared with a figure of nearly six hours a week in 1997

E.       chores, that figure growing to nearly six hours a week in 1997

这一题选B,当时大家的讨论结果是,分号隔开的两个句子时态无逻辑关系.但是下面PREP的这题选D明显的表明分号前后句子间时态有关系啊..请教能想通的同志们.谢谢谢谢请大家都来讨论~

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

我是按意思去理解后面道题的

we have now realized, though, that emissions of industrial chlorofluorocarbons deplete the ozone layer. 是对前面意思的一个转折，讲我们现在发现了那个emission of industrial chlorofluorocarbons 还是对ozon layer 有损耗。

再看前面，明显就是跟后面意思是相反的，而这个是以前的理解。  现在的看法用的是 we have前面用had 就是对的。 

再说where后面的 it:   D 选项的it 指代的是ozone layer 而E中指代的是后面的从句 ，所以综上应该选D。

第一个句子我的理解是由于有by 1997, 而1997 已经过了，这是个很明显的过去完成时标志，再加上本身比较的是figure， 所以就选B了。

个人意见仅供参考，  我也是正在挣扎着的。。。

再顶...希望有人来