Don't come into the lab________ you are asked to.

问题描述:

Don't come into the lab________ you are asked to.
Don’t come into the lab ________ you are asked to.
A.unless B.until C.because D.since

Don't come into the lab (A.unless) you are asked to.
如果没有叫你的话,就不要进这间实验室.
unless,除非,相当于if not.