Remember that a biotic factor is a living component in an ecosystem that affects the population of another organism. So that means that the answer is B.
Association between all the living things on earth
I think the answer would be a
Radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium.
c, 22,800 (4 half lifes, 1/2, 1/4, 1/8, 1/16)
