2019年mpacc考试英语真题——连词347

{01}People living in the desert choose to keep their ancient lifestyles and customs,_______  people in cities
throw away their cultural traditions.
A.when
B.if
C.unless
D.while
解析：
本题选D。

{02}I was about to go to bed ___ the bell rang.
A.as
B.while
C.when
D.since
解析：
本题选C。