Most hormones of the endocrine system are regulated by a .
Correct Answer: C
Rationale: The correct answer is C: negative feedback mechanism. This is because the majority of hormones in the endocrine system are regulated by a feedback loop that maintains homeostasis by inhibiting further hormone production when levels are too high and stimulating production when levels are too low. This negative feedback mechanism ensures that hormone levels remain within a narrow range.
A: hormone-gene complex is incorrect as hormones are not primarily regulated by direct interactions with genes.
B: hormone-receptor complex is incorrect as receptors are involved in hormone action, not regulation.
D: positive feedback mechanism is incorrect as it would lead to an amplification of hormone production, which is not typically seen in the endocrine system to maintain stability.