What is the main function of the immune system?

A. to circulate blood cells
B. to destroy pathogens
C. to secrete tears
D. to keep the skin moist

to destroy pathogens

Explanation:

the immune system helps fight off unwanted bacteria & anything your body doesn't recognize. whenever you're sick, your immune system is fighting off your sickness

d is the correct answer.

b is incorrect because it makes food by itself

c is incorrect because us humans don't know how to produce their own food using the sun like plants.

a is incorrect because consumers can depend on carnivores for eating food for consumers to eat the dead organism. same thing with omnivores.