they are 可以简写成they're,那么these are为什么不能简写成these're

they are 可以简写成they're,那么these are为什么不能简写成these're whose books are these?They're t______ -Are these coats_____ -Yes,they're ours. --What are these?--They're watchs.改错 They're eyes.These are feet. ( )these( ) ( No,( ) not ( ).( ) ( )are they?They're ( ).括号里 What are these?（）are maps.A.These B.They C.It D.They’re H m are these trousers?They’re 400 yuan. These are green balls and they're r__ Are these bags heavy?No,they ' re _____. These books are the twins'.They're ours 英语:These shoes are on clearance.They're( ).