What Is Characteristic of a Thermal Inversion

Multiple Choice

What is characteristic of a thermal inversion? 

A)  Thermal inversions last only a few minutes to a few hours. 
B)  Thermal inversions exacerbate pollution problems. 
C)  Thermal inversion occurs when a layer of cold air prevents warm air from rising. 
D)  Normally, cool air near the Earth's surface expands and rises, carrying pollutants higher into the troposphere.