求教一个GWD的语法题目

ppp033

Discussion of greenhouse effects has usually focused onwhether the Earthwould warm and by how much, but climatologists have indicated all along that the most obviouseffects, and those that would have the largest impact on people, would beextremes of temperature, precipitation, and storminess.

A.   the most obvious effects, andthose that would have the largest impact on people, would beextremes of temperature, precipitation, and storminess

B.   the effects that are the most obvious ones,extremes of temperature, precipitation, and storminess, would be thoseimpacting the moston people

C.   those effects to have the largest impact onpeople, extremes of temperature,precipitation, and storminess, are what are the most obvious effects

D.   extremes of temperature,precipitation, and storminess, the most obviouseffects, that they would have the largest impact on people

E.    extremes of temperature, precipitation, andstorminess, which are themost obvious effects, are those to impact the most on people

我很想知道D选项里面的，  that they would```  中， they为什么指代歧义？