Final answer:
The Appendix (C) is not part of the endocrine system; this system includes glands like the thyroid, adrenals, and pituitary, which produce hormones to regulate various body functions. Therefore, the correct option is C.
Step-by-step explanation:
The part of the endocrine system that is not listed is the Appendix (C). The endocrine system is comprised of glands that produce and secrete hormones, which regulate the body's growth, metabolism, and sexual development and function. The glands in the endocrine system include the thyroid, adrenals, and pituitary, among others. However, the appendix is not considered a part of the endocrine system as it does not produce hormones that regulate body functions.