Is this your pen Yes,I think it's her pen.

这句话的意思是
这是你的钢笔吗?是的,我想这是她的钢笔.
如果这样翻译过来肯定就是错的,那么这道题有两种改法：
1.把yes改成no:
is this your pen?no,I think it's her pen (hers)（这里her pen
可以用 hers 来代替）
2.把her 改成my
is this your pen yes,I think it's my pen(mine)( 这里my pen
可以用mine来代替）