3. He went to a disco, ________ (where/which) always gave him a headache.
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4. He’s a writer ________ (whose/which) books have been translated into one hundred languages.
5. This city, ________ (which/where) is very big, is also very friendly.
在非空的树中,根结点________
A. 不存在
B. 有且只有1个
C. 不少于1个
D. 不少于2个
在非空的树中,叶结点________
A. 不存在
B. 有且只有1个
C. 不少于1个
D. 不少于2个