Experts believe that language learning is a process skills are more important than gramma

Experts believe that language learning is a process skills are more important than grammar rules.
A. whose
B. when
C. of which
D. in which

A. whose B. whenC. of which(答案→)D. in which解析：考查定语从句：先行词是a process，定语从句中缺少地点状语，用where或in which引导定语从句，句意：专家相信语言学习是个过程，其中技能要比语法更重要。选D。

就是这个解释