牙肉萎缩怎样治疗:I've worked with children before ,so I know what to expect in my new job.是什么意思？

I've worked with children before ,so I know what to expect in my new job.是什么意思？ I've 是什么? I've怎样发音 I have worked 和 I had worked 各自的意思 I've just arrived by train. I've Never Been To Me I've是什么的简写？ I've 的歌有哪些 [I've sound 音乐联盟]是什么？ I've been miles from nowhere