From this diagram of fossils (sorry it’s a bit blurry) which layer is the youngest and which layer is the oldest? How do you know?

The bottom layer is the oldest, and the top layer is the youngest

Explanation:

As time goes on more and more sediment gets piled onto a certain place, meaning the oldest fossils will keep getting deeper and deeper

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.