—— What’s she doing for vacation?——She’s _____ Beijing. 

 Beijing ________ a lot over the years. Now it has become one of the biggest ______ in the world.

—Look at the clouds! I think it’s going to _______. —Oh, we have to run home.         

While the boy ______ down the street, the UFO _____ . 

I began watching here an hour ago, but now nothing _______ yet.