Name the respiratory structure in the amoeba

The respiratory structure of an amoeba is called the mitochondria. This is because amoebas are eukaryotes and use mitochondria to respire.

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.