Radon Gas Can Accumulate in People's Homes and Pose a Serious

Radon gas can accumulate in people's homes and pose a serious lung cancer risk. What is the source of the radon gas?

A) radioactive decay of uranium minerals found in rocks and sediment
B) breakdown of natural gas deposits
C) byproduct from the breakdown foam insulation used in home construction
D) contaminated groundwater surrounding nuclear power plants
E) byproduct from the breakdown of asphalt roofing shingles used in home construction