b. They are carried throughout the body in the bloodstream, and each hormone affects target cells that have receptors for it.
Explanation:
Hormones are secreted by hormonal glands after they get signals to secrete or release the hormone. Then these hormones are carried by the bloodstream to their destination. Each hormone has its target organ or tissue which do not response to other hormones because it the cells in those tissue have specific receptor which binds to specific hormones.
For example, luteinizing hormone in male is produced by the pituitary gland which reach to the testis through blood and influence the Leydig cell to release testosterone. So Leydig cells have receptors for LH not for insulin hormone so it binds specifically to LH hormone. So the correct answer is b.
