7. Complete the definitions with the words from the box.
aquifer • fresh water • ground water • lake • river • salt water

a. ____________ : a natural wide flow of fresh water into the sea, a lake, or another river

b. ____________ : a large area of water surrounded by land and not connected to the sea except by rivers or streams:

c. ____________ : underground water that is held in the soil and rocks

d. ____________ : sea water

e. ____________ : water that does not contain any salt, especially water found in lakes and rivers

f. ____________ : a layer of rock or earth that contains water or allows water to pass through