两道PREP题时态问题求助

liuyingxin

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  
答案为D

147.Australian embryologists have found evidence that suggests that the elephant is descended from an aquatic animal, and its trunk originally evolved as a kind of snorkel.

(A) that suggests that the elephant is descended from an aquatic animal, and its trunk originally evolved
(B) that has suggested the elephant descended from an aquatic animal, its trunk originally evolving
(C) suggesting that the elephant had descended from an aquatic animal with its trunk originally evolving
(D) to suggest that the elephant has descended from an aquatic animal and its trunk originally evolved
(E) to suggest that the elephant is descended from an aquatic animal and that its trunk originally evolved
答案为E

同样跟在现在完成时后面，为什么一题用过去完成时而另一题用现在时呢？

keaidebingbing

同问！！！