请帮解这选择题 关于比较的 she is

请帮解这选择题 关于比较的 she is _____ a fool than i thought.
she is _____ a fool than i thought. she is quite smart.
A more of
B more than
C less of
D less than
答案是C 我不太明白这几个结构 尤其是D为什么不对 ,请帮解释一下 谢谢啊

than后可以加名词：比如more than a beautiful woman（人美心灵更美之类的）
关键是后面有个than了,前面就不用了.
如果是she's less than a fool就可以.不过语义也有点不同.这句说明这个女孩虽然傻,但是也没有傻到白痴境界.