新概念英语定语从句

I want to buy the books *which(或that）are* on the counter.

This is a photograph *which(或that)--可省* I took during my trip to london.

This is the best film *which(或that)--可省* I have ever seen.

I want to buy the books which on the counter.
this is photograph that i took during my trip to london
this is the best film that I have ever seen

books that/which
that
that先行词前有表示最高级或者序数词或者VERY等词要用THAT