These blue pens are Cindy's,and those red pens are ___________,too

问题描述:

These blue pens are Cindy's,and those red pens are ___________,too
这里应该是one还是it?
Does Mary have a small mouth?
No,she has a wide _______.
打错了

These blue pens are Cindy's,and those red pens are _【hers】__,too

Does Mary have a small mouth?
No,she has a wide __【one】.为什么是one呢?两句mouth都是指的一个啊,老师说同类用one,同一个用it一般是用a+形容词+one 来代指事物,it没有这种用法