**NEED TODAY** The picture shows a protist, which is a single-celled organism. The structure labeled X on a single-celled organism is most similar to the A skin of a multi-celled organism. B brain of a multi-celled organism. C veins of a multi-celled organism. D stomach of a multi-celled organism.

i'd say that the moon rock is about 2.2 billion years old.

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.