I would appreciate it _____ you call back this afternoon for the doctor's appointment.

问题描述:

I would appreciate it _____ you call back this afternoon for the doctor's appointment.
A,until B.if C.when D.that 请问应该选哪个?我怎么觉得BC都可以呢?

B
这是句型
I'd appreciate it very much if you could do sth,意思:如果你能做什么的话,我将不胜感激.