— What do you think of teaching, John?

— I find it fun and challenging. It is a job ______ you are doing something serious but interesting. [ ]

A. what

B. which

C. where

D. that

行政复议调解未达成协议或者调解书生效前一方反悔的，行政复议机关应当重新审理原具体行政行为。