一When did you learn the news that Obama made a trip to Canada as President?一 ____ was on my return．

I told your friends how to get to the hotel, but perhaps I ____have driven her there.

I’m sure Wang Lin is ____ to come to my aid this afternoon.

--- Where is the post office ? --- Go to the ______ and you’ll see the post office ______ the street．

With a lot of difficult problems ______, the newly-elected president is having a hard time.