What is responsible for telling cells how to behave

Cellular differentiation and signaling

Explanation:

Cells specialize in their functions due to the process of differentiation, transforming embryonic cells into new cells with specific morphology and physiology.

The behavior of cells for different functions is due to gene expressions and also thanks to receptors on the surface and inside the cell.

These receptors bind to signaling molecules, establishing communication between the nervous system and the others, ensuring the specificity of cells.

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.