there were dirty marks on her trousers which she had wiped her hands.1这句话先行词是?2将这句话分为两句

问题描述:

there were dirty marks on her trousers which she had wiped her hands.
1这句话先行词是?2将这句话分为两句

1, 先行词是 her trousers
2, (1)There were dirty marks on her trousers.
(2)She had wiped her hands on her trousers.

我觉得which前应该有on,或者把which改为where.
先行词是裤子.
There were dirty marks on her trousers.She wiped her hands on her trousers.