--Why does the lake smell terrible?    ---Because large quantities of water ______.

Where ___ you ____?

80,000 yuan ________ a lot of money, but it’s far less than we need.

Either you or one of your students ______ to attend the meeting that is due tomorrow.

Our school had about 20 notebook computers but only one-forth_____used regularly. Now we have 50 working all day long.