许多同学都有自己的电子邮箱，如168@sina.com, pgbook@ 163.com, hifriend998 @ 126.com 等。请问其中的@表示什么意思，该怎么读

You parkhere! It’s an emergeney exft.

Do you really want to borrow the old roomwhich is empty _____a broken desk and a chair

Mary’s room is a bit untidy，so she’ll tidy it ．

Being not far ________ the sea, London is famous________ its fog.