标题: 两道PREP题时态问题求助 [打印本页] 作者: liuyingxin 时间: 2011-10-10 18:03 标题: 两道PREP题时态问题求助 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