Question

帮我解答一下这道英语题吧!!!!

The students was required to describe a certain illness,____ turned out to be OK.
A.whose description B.of whose description
C.his description of it D.his description of which
答案是D.但是我不明白D中为什么要加of which；又为什么不选A

Answer 1

同意阿跑。