Humans need for cell membranes, but cannot produce them. a. saturated fatty acids b. unsaturated fatty acids c. proteins d. triglycerides

The answer is triglycerides.

haploid cells;

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.