If the sum of radius and height of cylinder is21 cm and CSA is 616 cm Find TSA

the answer is d (apex) good luck : ))

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.