24-23 Discussion of greenhouse effects has usually focused on whether the Earth would warm and by how much, but climatologists have indicated all along that the most obvious effects, and those that would have the largest impact on people, would be extremes of temperature, precipitation, and storminess.

A) the most obvious effects, and those that would have the largest impact on people, would be extremes of temperature, precipitation, and storminess.

B) the effects that are the most obvious ones, extremes of temperature, precipitation, and storminess, would be those impacting the most on people.

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

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

E) extremes of temperature, precipitation, and storminess, which are the most obvious effects, are those to impact the most on people.

KEY:A

I don't understand the structure of "A"

Hope somebody give me some advice!

Thanks!

the most obvious effects, and those that would have the largest impact on people, would be extremes of temperature, precipitation, and storminess.

=the most obvious effects would be extremes of temperature, precipitation, and storminess. and those(effects) that would have the largest impact on people would ALSO be extremes of temperature, precipitation, and storminess.

24-23. Discussion of greenhouse effects has usually focused on whether the Earth would warm and by how much, but(前後對比) climatologists have indicated all along that(引導後面子句) the most obvious effects, and those(most obvious effects) that would have the largest impact on people(插入句可忽略), (most obvious effects)would be extremes of temperature, precipitation, and storminess(and 並列三個).

總的來說就是but 前後各是一個主句帶一個從句，前後句意約略相反