T-18：to and fro 来来回回
A:Why are you walking to and fro in the room?
A:你为什么一直在房间里来回地走啊？
B:I'm worrying about the children. After all this is the first time they're been out without us.
B：我为孩子们担心，毕竟他们是第一次离开我们，走出家门。
A:Don't worry. They are grown-ups.
A：别担心，他们已经长大了。
B:I know. But I couldn't help.
B:我知道，但还是情不自禁。
