His best novel was written in ( ) he called the sweet new styl

His best novel was written in ( ) he called the sweet new style of the language.
A、that
B、where
C、what
D、which
【正确答案】：D
【题目解析】：in which 引导定语从句，句子含义是他最好的小说是以一种是他称之为小清新风格语言写成。