The school has developed an on­line system________ students can choose their own teachers.

The new iphone 5 costs so________that I don’t think astudent can________ it.

There is no light on, they ____ be at home. [ ]

Our school was going to send a teacher to Xinjiang . I was the first person _______ to go.

_____ his return from Europe, he set to work on the project[ ]