I could hardly recognize her at the first sight because she was________in such a large skirt and________sunglasses[ ]

I bought this dictionary two weeks ago. —-You mean you __________ it for half a month.

He always works hard, but__________, hedidn’t pass the exam.

Can she play the guitar or the violin–______. But she can play the drums.

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