Its true to say that modern humans are, a, hominids b, hominins c, primates d, all of the above

hominids

Thumbs are called opposable because they can be moved around to touch the other fingers, giving the ability to grasp things. 

This ability is shared by Old World monkeys, apes, and humans. 

Hominin is the group which consists of modern humans, extinct human species and all immediate human ancestors like those in the genra Homo, Australopithecus, Paranthropus and Ardipithecus

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.

i think it’s c but i might be wrong. if i am let me know! have a good rest of your day as well!