Which system covers the external surface of the body and manufactures vitamin D: A) endocrine system
B) integumentary system
C) nervous system
D) lymphatic system

B the integumentary system

Explanation:

Largest body system and comprises the skin and the appendages which acts to protect the body from a variety of different kinds of damage's Examples such a as lack of water or abrasion from the outside.This system includes hair,scales,feathers,or even nails.this system may help keep your body afloat and regulate temperature.

answer; i believe that the correct answer is (lung);

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.