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题目内容
（郑州工程技术学院-大学英语（2）.）
20.
Living in the desert involves a lot of problems, ____water shortage is the worst.
(A) not to mention
(B) of which
(C) let alone
(D) for what
Living in the desert involves a lot of problems, ____water shortage is the worst.
(A) not to mention
(B) of which
(C) let alone
(D) for what
参考答案