You must look around when you go _____ the street.[ ]

.Put it down，Tom. You mustn’t read _letter.

book on the desk isuseful one.

It is safe to eat chicken that________fully, but most people still dare not do that because of the H7N9bird flu .

Jack, could you help me ________ these pictures on the blackboard? It may help us know more about the hazy weather. (雾霾) — With pleasure.