don't buy cups or boxes which can be used only once.为什么用which?what呢?boxes不是复数吗可用which

don't buy cups or boxes which can be used only once.为什么用which?what呢?boxes不是复数吗可用which
don't buy cups or boxes which can be used only once.为什么用which?what呢?boxes不是复数吗可用which

don't buy cups or boxes which can be used only once.为什么用which?what呢?boxes不是复数吗可用which
which引导得定语从句修饰前面的box,cups.和box单复无关.what不能用来引导定从,一般用来引导主从

which后面的是定语从句，修饰cups or boxes
也可以用that
不能用what