【题目】It is impossible for him to change his mind once he has ________ doing something.
A. depended on B. debated on
C. relied on D. decided on
在线课程【答案】D
【解析】考查动词短语辨析。句意：一旦决定做某事，他是不可能改变主意的。depend on“依靠，取决于”；debate on “就某事辩论”；rely on“依靠”；decide on“决定，选定”。根据语境，故选D。