One way for students to prevent H7N9 flu virus is to openthe windows of the classroom to allow the air to ________

Short hair is back ________ this year.The female workers in my office all had their long hair cut.[ ]

u stay here longer, you may. But you leave before this weekend.

She shouted with friends and then stood up _______ she could see the film stars clearly.

____ have known the truth, or shewould have told us.