—Listen! Someone ____________ on the street.
—Singing? He is crying.
A. is singing B. sing C. sings
The story _______ about fifty years ago.
| A．was happened | B．happened |
| C．was happening | D．would happen |
He arrived____ London ____ a cold winter night.
| A．at; at | B．in; on | C． in; in | D．\; on |
When I walked past her room, I heard her _______ an English song.
| A．singing | B．was singing |
| C．sang | D．is singing |
Keep the machine _______, and you will know how it works.
| A．run | B．to run | C．running | D．runs |
—What was Tom doing _______ it was raining?
—He was doing his homework in the bedroom.
| A．since | B．while | C．when | D．if |