1.She discovered that the old man was _____ hearing.

1.She discovered that the old man was _____ hearing.
A.hard at B.hard with C.hard of D.hard in
2.He had no idea how much a room in this hotel _______.
A.was charged B.charged C.was charged for D.charged for
我知道charge的用法是charge sb money for sth
难道还可以charge sth for money吗？
还有，第一题书上答案是C，怎么回事啊?