There’re so many kinds of tape-recorders on sale that I can’t make up my mind _______ to buy.
A:what
B:which
C:how
D:where
关于我国地形、气候、河流之间的关系,说法正确的是( )
如图为肺泡内的气体交换示意图.下列相关叙述不正确的是( )