Question

The pen ________ he is writing is mine.

A．with which	B．in which
C．on which	D．by which

Answer 1

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。