．—I didnot know you were good friends．—You___．I have known her since she moved here．You were abroad then．

So fast _____it is difficult for us to imagine its speed.

It is _______ of the students to stay up readingtill late night before the final exam

______ a phone is of great help, I don’t think it’s a good idea to spend too much time on it.

Shall we go sailing in the sea tomorrow—______ It’s reported that there will be a hurricane(飓风) tomorrow.