How is a class system different from a caste system?

A class system is a more smooth system, caste is more of a system that changes consistently.

Explanation:

"Class system is typically more fluid than the caste system or the other types of stratification and the boundaries between classes are never clear-cut. Caste system is static whereas the class system is dynamic. ... In the caste system, individual mobility from one caste to another is impossible."

answer: - b cells

explanation: -

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.

answer; i believe the correct answer to the above question is ( friction)