高等继续教育 / 经贸英语
正确率：100%
题型描述: 单选题
You must clearly understand that ＿＿＿＿ you can supply us with the best quality in every case, we shall have to fill our requirements elsewhere.
A.when
B.whether
C.until
D.unless
You must clearly understand that ＿＿＿＿ you can supply us with the best quality in every case, we shall have to fill our requirements elsewhere.
A.when
B.whether
C.until
D.unless
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