the only person i have ever known ___a skeleton in the cupboard...

the only person i have ever known ___a skeleton in the cupboard...
a. he had
b. lf having
c.that he has
d. to have
答案：d
拜托达人,解释一下为什么~
原句来啦~~~
the only person I know who has a skeleton in the cupboard is George Carlton ,and he is very proud of the fact. ~