but I don't know what ____for them.A.buy B.buying C.to buy急.

but I don't know what ____for them.A.buy B.buying C.to buy急.
but I don't know what ____for them.A.buy B.buying C.to buy
急.

but I don't know what ____for them.A.buy B.buying C.to buy急.
C
动词不定式与疑问词连用
意思是：
我不知道给他们买什么?
加油!不明白再问!

应该填写：
C
what to buy 去买什么
但我不知道去给他们买什么
~~~~~~~~~~～～~~~~祝你进步，如对你有帮助，请及时采纳~~~~~~~~~~~~~~~~~~

C.to buy
我也不知道给他们买点什么好。

c谢谢