In HIV-infected patients, there is a gradual loss of CD4+ T cells over time. These cells, also called T helper cells, organize the immune system's attack on disease-causing invaders, like Salmonella.
Answer;
C. Poor farming techniques that killed the soil were combined with drought.
Explanation;
-The Dust Bowl was caused by several economic and agricultural factors, including federal land policies, changes in regional weather, farm economics and other cultural factors.
-After the Civil War, a series of federal land acts coaxed pioneers westward by incentivizing farming in the Great Plains.