Answer:
D. Steroid hormones
Explanation: This could be easily searched on Google, however a good way to remember this is to remember that cholesterol is a sterol, and the word "steroid" is derived from that word. A is incorrect obviously, because protein hormones and steroid hormones are two different things. B is also incorrect, because glands are the producers of the hormones, not the hormones themselves. C is incorrect because an exocrine is a type of gland that releases its products through ducts rather than directly through the bloodstream, so D is the definitive answer.
