Which part of a plant is found in the center

The pistil usually is located in the center of the flower and is made up of 3 parts called the stigma, style, and ovary.

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.