The Doha Round of WTO talks in Geneva last month collapsed as efforts to reach a compromise on the point at which developing countries could raise import tariffs on farm products failed.
主句：The Doha Round of WTO talks collapsed 简单句：主+谓
last month 时间状语
as efforts to reach a compromise on the point at which developing countries could raise import tariffs on farm products failed. as引导的原因状语从句
efforts 从句主语
to reach a compromise on the point 不定式短语作定语修饰主语efforts
at which developing countries could raise import tariffs on farm products 定语从句修饰point
(at which相当于at the point,在定语从句中作状语；developing countries主语,could raise谓语, import tariffs on farm products宾语)
failed 原因状语从句的谓语
at不能去除,因为从句主谓宾成分齐备,引导词只能做状语,at which 可以作状语,which疑问代词不能做状语.
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