The correct response is: They are carried by blood.
Hormones reach target cells by being carried by blood. Blood serves as the transportation system for hormones throughout the body. When hormones are released by endocrine glands, they enter the bloodstream and travel to their target cells. As blood circulates around the body, hormones are delivered to the specific tissues or organs that have receptors for them. These receptors allow the hormones to bind and initiate a response in the target cells, which can include various physiological effects. So, the correct answer is "They are carried by blood."
