I need help on this one and another one pls help

I think the last option which is plant cells

Explanation:

because their wavelength is from 450-475 nm and around 650-675 nm.

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.

the answer is cell division : )