C.for you to pretend （掉了个for),
这是不定式的复合结构作真正主语的
如果选项C 就是这样的,那就只能选A了,your pretending that you didn't know the rules 这个动名词的复合结构作真正主语.难道是书本印错了。。。这个结构一般用于 It is no use/good (one's doing sth)It is useless for sb to do sth. 当然 It is useless one's doing sth 也没错， 但不常见。