Don’t you know your computer has been infected with viruses?— Really, no wonder it hasn’t ________ as well as before. [ ]

He looks upset.Let’s try to _____.

The bus hit against a tree in the fog and ______to the deep valley，with ten passengers killed and twenty wounded.

You _______look before you cross the road.

There is a big library in our school,and this is I often go to get the latest information.