This is one of the two main types of white blood cells that is an essential parts of the immune system and directly attacks antigens. it is produced in bone marrow, matures in the thymus, and travels in the blood to other tissues, such as the spleen, tonsils, and lymph nodes.

What sentence best supports the statement that hormones are involved in the regulation of homeostasis? a. the hormone erythropoeitin increases the production of red blood cells when oxygen levels are low. b. the hormone oxytocin promotes labor contractions of the uterus during childbirth. c. the hormone melatonin induces sleep and its production is slowed by exposure to light. d. the hormone cortisol suppresses the immune system and is produced when the body is under stress.