【题目】He wrote many children's books, nearly half of____ were published in the 1990s.
A.whom
B.which
C.them
D.That

【答案】B
【解析】句意：他写了许多儿童书籍，几乎一半在20世纪90年代左右出版。先行词是books，定语从句中of缺少宾语，故选B项，