Prep2-8
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 ans D 我想问的是形式主语的问题 题中where it has long ...的it形式主语指代的是什么啊? 一到形式主语我就有点犯晕~ |