Why can it take soil thousands of years to form

The reason is that soil is often derived from rock. The rock has to be broken into small pieces first. This happens by physical weathering: things like freezing and thawing in colder climates, and chemical weathering in warmer climates

It may take hundreds to thousands of years. It will take longer in colder and drier regions than in warmer and wetter regions. This is due to the soil forming processes such as translocation and transformation being slower in cold and/or dry areas.

Explanation:

Hope this helps:)

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.