The total quantity of water on Earth________.A.ha

.________quantities of water are being used nowada

According to the old－timers, on two occasions ______.A．the water of the lake turned redB．l

Without the sun s light______the earth s surface, no life could exist on the earth.A．warms

All his attention was ______ on one thing only—how to solve the problem of water shortage.

Investigations______ the origins of life on the earth have shown that, given earth－like co

Most of the fresh water on Earth________.A.is in