Most birds find it safe to sleep in the
题型:选择题
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.where
D.unless
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.where
D.unless