解释英语语法
(1)You'vejustmissedit.
You'vegivenmethewrongcase.
I'vehurtmyback.
Ihavejustarrivedinscotland.
为什么都用have?不用be动词?
(2)Hesayshe'sjustarrivedinscotland.
's省略的是什么?为什么是?