iI'll show you a store _____you may buy all____you need C where,which D.in which,/为什么选D?C有什么不对吗?

iI'll show you a store _____you may buy all____you need C where,which D.in which,/为什么选D?C有什么不对吗?
iI'll show you a store _____you may buy all____you need C where,which D.in which,/
为什么选D?C有什么不对吗?

iI'll show you a store _____you may buy all____you need C where,which D.in which,/为什么选D?C有什么不对吗?
因为all做先行词时,其后的连接词只能用that,而且在从句中做宾语,that当然也可以省略.