33. 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,
如果选E的话，我觉得原文的意思就变了。文中说的是a derivative of the madagascar periwinkle是传统与现代的结合，, 但是E 说的是M本身是传统草药与现代医疗的结合。
所以我选了C。 derivative,也有名词的意思-衍生物。
请指教！ | 
