The chemical messengers that are secreted by glands, enter the bloodstream, and travel to distant target sites to regulate their functions are known as the chemical messengers that are secreted by glands, enter the bloodstream, and travel to distant target sites to regulate their functions are known as bases.
a) hormones.
b) organelles.
c) enzymes.

Such chemical messengers are known as hormones.

Explanation:

Hormones are majorly responsible for stimulating the blood cells that carry the stimulus further to the intended organs. The blood cells promptly respond to the secreted hormones as they have receptors that are designed to receive the message (or the stimulant) from them. There are three major types of the functioning of hormones known as endocrine action, paracrine action, and autocrine action. The endocrine action is responsible for the distribution of hormones to distant cells. Paracrine action refers to the distribution of hormones to the cells in the neighborhood of the gland. Autocrine action is responsible for distribution of hormones among the cells within the gland.