问题
选择题
He met many problems------ he was going over his lessons.
A．before
B．as soon as
C．since
D．while
答案
D
考查连词。此句中主句中是一般过去时，而从句中是过去进行时，故用while。
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He met many problems------ he was going over his lessons.
A．before
B．as soon as
C．since
D．while
D
考查连词。此句中主句中是一般过去时，而从句中是过去进行时，故用while。