i couldn'd decide--- a.what to buy b.which oen to buy c.to b

从语法上看,C和D直接是错的
如果前面具体说了可以在几件东西里挑一件的话,就选B
如果没有具体的范围,就选A
比如,我说我家有茶水和果汁,我可以问你,Which one do you like?
如果直接问客人想喝什么,说What do you like to drink?