◎ 题干
If you don't learn something useful, you will feel sad ______ you are old.
[     ]
A. what
B. when
C. which
D. why
◎ 答案
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“If you don't learn something useful, you will feel sad ______ you are old. [ ]A. what B. when C. which D. why …”主要考查了你对  【从属连词】【状语从句】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。