Asymbiotic relationship where both of the co-existing species benefit from the interaction is called
commensalism
parasitism
mutualism
communism

mutualism is a correct answer.

Explanation:

A symbiotic relationship where both of the co-existing species benefit from the interaction is called  mutualism.

Mutualism is a positive interaction between the two organisms of different species in where both organisms get benefit from each other.

Mutualism is a symbiotic relationship where both the coexisting species benefit each other without doing any harm to each other and they depend upon each other for survival.

Example of  mutualism : Bacteria and Human

Bacteria present in our intestine shows the symbiotic relationship as the bacteria present in the intestine help in digestion of the food and during this process they get food.

its the cell wall and the they are unique to plant

i think the answer is a.keratin is the pigment responsible for skin color.