— Why does the lake smell terrible?— Because large quantities of water ____.

The number of the students in our school _____ than that in theirs.

While a huge amount of money ___been spent stopping pollution , large quantities of water_    _still heavily polluted．

Jane and I ____ twelve. My sister ____ ten.

—How much are the two pairs of shoes?  —They are not expensive. I think fifty dollars ______ enough.