Which of these changes to a modern lifestyle would promote the development of more-sustainable practices in the world food system
a. eating more processed foods
b. buying fresh fruit year-round
c. switching from beef to soy
d. eating fresh vegetables year-round

c. switching from beef to soy

Explanation:

Switching from beef to soy shall lead to the curbing of lifestyle diseases such as obesity.

At the same time, soy shall provide the nutrients that were needed by the body and could be obtained from beef.

Beef is much expensive compared to beef, thereby, there shall be experienced  low expenditure compared to beef.

Therefore the switching from soy to beef shall be a more sustainable food system.

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.

the answer would be knowledge about cars!