A book that weighs 5 newtons is sitting on a table 1.5 meters above the floor. How much gravitational potential energy does the book have? 6.5 joules
4.5 joules
7.5 joules
3.33 joules

7.5 this is the right answer.

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.