问题:
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
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 |
参考答案: