that was 可以等于that's吗

that was 可以等于that's吗 that was 可以缩略成that's that's 可以做that was的缩写么? that's =that is or that was?rtthat's =that was? that's= that was?that's sometime= that was? ……and that's what I was doing when Charlie came home.此处’s是is还是was?was可以缩写为’s吗? it's not surprising that中的that可以省略吗? It s difficult to say-----this portrait was painted by 横线处可以填that吗为什么呢如果填who 那么that不是可以替换who吗。 The man (that) I met yesterday was Tom’s father.that为什么做表语?我觉得是宾语吧 可以换作which吗? That’s changed since I was here.That’s changed since Iwas here.这个句子中,'s可以改成was么?为什么？ It s difficult to say-----this portrait was painted by横线处可以填that吗为什么呢 “So that's what it was! That day was April Fool's Day It seems（that）he was late for the train!表语从句,that可以省略吗? 这里that与which可以替换吗?she means the one that was bought yesterday. it happened(chanceed) that he was out 中的that可以省略吗? that's great 中's可能是was的缩写吗 was能缩写成's吗?that's great 有过去式吗? that's almost half od the world's population.为啥用that?it可以吗