问题补充:
The pen he is writing is mine.
A. with which
B. in which
C. on which
D. by which
答案:
A. with which
B. in which
C. on which
D. by which
解析:with which是“介词+关系代词”结构,常用来引导定语从句。with有“用”的意思,介词之后只能用which,不能用that,with which在定语从句中作状语,即he is writing with a pen。