17.---May I surf the Internet tonight? --- No, you ______.You must do the exercises.
Though they had a meeting yesterday, there is still much that remains______.
The students expected there ________ more free time before the test.
Does the way you thought of ________ the water clean make any sense?
The bridge is so important to the people here that once ________ it must be carried out without delay.
They tried to prevent the damage ________ their cattle.