Aquifers and wells are two major sources of
a. groundwater
c. rivers
b. lakes
d. none of the above

a. groundwater

Explanation:

Aquifers and wells are the two major sources of groundwater. A groundwater is a underground reservoir of surface water that seeps into the pores of the soil and that of the rocks. The water in the groundwater comes from the rain, river, agricultural irrigation and from other freshwater sources. This water remains uncontaminated by the external pollutants and chemicals unlike open water bodies.

gas

explanation:

smoke is the matter of a gas