2019年mpa考试英语真题——连词539

{01}I didn"t manage to work out the problem _____ the teacher had explained how.
A.until
B.unless
C.when
D.before
解析：
本题选A。

{02}We had to wait half an hour _____ we had already booked a table.
A.since
B.although
C.until
D.before
解析：
本题选B。