Which structures deliver blood to the heart from the body?

Blood Vessels, I believe.

I think that it'll be the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium.

Explanation: Because, the pulmonary vein empties oxygen-rich blood, from the lungs into the left atrium.

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.

after a the power stroke, adp is released, but the cross-bridge formed is still in place. atp then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.