Question

The pen ______he is writing is mine.

Answer 1

答案A
.
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.

Answer 2

a
因为定语从句里的he
is
writing缺了介词，应该是he
is
writing
with
the
pen.
d
因为定语从句里的my
father
works缺了介词，应该是my
father
works
with
the
engineer,