问题
选择题
Most birds find it safe to sleep in the trees, but they have eggs or young chicks, they don't use a nest.[ ]
A. why
B. how
C. unless
D. where
答案
答案：C
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Most birds find it safe to sleep in the trees, but they have eggs or young chicks, they don't use a nest.[ ]
A. why
B. how
C. unless
D. where
答案：C