---How did the accident happen? ---You know, it ________difficult to see the road clearly because it_________. 

Mr. Black isn’t here. He ________ to Chongqing.

---Excuse me. Where is Lily? ---Oh, she _______ the volleyball match on the playground when I saw him just now.  

I will send you an e-mail as soon as I ______ in Canada.

 To solve the traffic problem, more and more bridges ____________ across the river every year.