When you are sleeping, you had better______ all the windows closed.
The Changjiang River is one of ________ in the world.
________ the party, we sang a song together.
It takes ________ half an hour ________ on my bike.
There ________ a football match between Class 1 and Class 3 next week.
—Excuse me, ________ is the library from here?—It’s about 5 minutes’ walk.