What happens when the diaphragm contracts? a. the volume of the thoracic cavity increases. b. the diaphragm rises. c. the volume of the thoracic cavity decreases. d. the rib cage moves down.

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.