请教2004-08-13

Most whole milk undergoes homogenization,_________  hot milk is pumped through vavles to break up and permanently disperse the fat globues.

A   a process

B   which process

C   a process in which

D   which is a process

为什么选C呢？D 为什么不对呢？

which is a process (          ) hot milk is pumped through vavles to break up and permanently disperse the fat globues.

空缺处少引导词。