Which of the Following Statements Is True

Which of the following statements is true?

A) Thermal inversion occurs when a layer of cold air prevents warm air from rising.
B) Thermal inversions exacerbate pollution problems.
C) Thermal inversions are temporary.
D) Normally, cool air near Earth's surface expands and rises, carrying pollutants higher into the troposphere.
E) Thermal inversions help prevent air pollution.