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题目内容
（兰州交通大学大学英语4）
7单选(2分)
The visitors tiptoed to the workroom_________ they should interrupt the painter’s work.
得分/总分
A.
provided
B.
unless
C.
if
D.
lest
The visitors tiptoed to the workroom_________ they should interrupt the painter’s work.
得分/总分
A.
provided
B.
unless
C.
if
D.
lest
参考答案