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1.        A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients, is cultivated in China as part of a program to integrate traditional herbal medicine into a contemporary system of health care.

(A) A substance derived from the Madagascar periwinkle, which has proved useful in decreasing mortality among young leukemia patients,

(B) A derivative, which has proved useful in decreasing mortality among young leukemia patients, of the Madagascar periwinkle,

(C) A Madagascar periwinkle derivative, which has proved useful in decreasing mortality among young leukemia patients,

(D) The Madagascar periwinkle has a derivative which has proved useful in decreasing mortality among young leukemia patients, that（E）

(E) The Madagascar periwinkle, a derivative of which has proved useful in decreasing mortality among young leukemia patients,

The correct answer is E, but my choice is D. Can anyone help me? 谢了。

D 显然错了，逗号后的that怎么也不对吧

选E的原因是："is cultivated" 的主语只能是 "The Madagascar periwinkle"。"A substance/derivative"是不能被cultivated(种植，养殖）的。所以cultivated的是periwinkle，而 proved useful 的则是 a substance derived from periwinkle。因此，E对。

供参考

弱问一下

我知道E优于C，应该选E

C有错误么？

derivative 不能被cultivate

不会。

a derivative of which 要一起看做是定语从句引导词。这是常见用法。