Arteries carry blood away from the heart. In all but one case, arteries carry oxygen-rich blood. The exception is the pulmonary arteries. They carry oxygen-poor blood away from the heart, to the lungs, to pick up more oxygen. Veins carry blood back to the heart. In all but one case, veins carry oxygen-poor blood. The exception is the pulmonary veins. They carry oxygen-rich blood from the lungs back to the heart.

Veins are the only circulatory vessels that contain valves. These structures contain valves because much of the pumping pressure that originated in the heart has been reduced by the time blood reaches veins, which return deoxygenated blood to the heart. The reduction of force can cause the blood to pool or move very slowly. Since veins rely mostly on gravity, blood flow force (originating from the heart), and muscular contractions to squeeze blood through them, it makes sense for them to have valves to keep blood from flowing backwards in between muscular contractions.

The pulmonary arteries are the only arteries that contain oxygen-poor blood because it carries blood into the lungs to be oxygenated. By definition, arteries carry blood away from the heart and veins carry blood to the heart. However, the pulmonary vein is the only vein in the body that carries oxygen-rich blood (from the lungs back to the heart to be pumped into the rest of the body) and the pulmonary artery is the only artery in the body that carries oxygen-poor blood (to the lungs to be oxygenated before being sent to the heart to be pumped into the rest of the body. The carotid artery is in the neck and delivers oxygen-rich blood to head. The femoral artery is in the leg and delivers oxygen-rich blood to the leg. The aorta is the main artery that delivers blood from the left ventricle of the heart to the rest of the body. 

Blood types are named according to the antigens present on the surface of a person's red blood cells, specifically the ABO and Rh antigens. AB+ blood has all three antigens and therefore none of the antibodies, meaning it can receive any blood type without having an immune reaction to the donor blood. 

O- blood is unique from the other blood types due to its lack of ABO and Rh antigens. Unlike A and B, O is used to denote no antigens rather than an "O type" of antigen. As a result, it can be given to any other blood type since there are no antigens on the red blood cells to have an immune reaction the recipients own natural antibodies. 

The function of the lymphatic system is to keep fluids out of the interstitium and connective tissue by returning it to the blood. Fluid leaks out of capillaries because of their thin walls. The lymphatic vessels collect this fluid and return it to the heart. When the lymphatic system is impaired, this fluid can accumulate in the tissue and cause swelling, known as edema.

Most of the lymph re-enters the venous circulation through the thoracic duct, and the volume is somewhere around a liter to a liter and a half per day.  

Deoxygenated blood enters the heart through the right atrium, where it then flows into the right ventricle. The right ventricle pumps the deoxygenated blood through thepulmonary arteries to the lungs, where it becomes oxygenated. Oxygenated blood returns to the heart through the pulmonary veins, which empty into the left atrium. Blood then flows into the left ventricle, which contracts to pump the blood through the aorta and toward the rest of the body.

In the circulatory system, the heart acts as the pump, the vessels are conduits allowing blood and lymph flow, and the transport fluid is the blood, which can deliver nutrients and oxygen to tissues and cells throughout the body. Thus, the primary purpose of the circulatory system is, as the correct answer choice states, to deliver oxygen to tissues and transport blood and lymph.

The respiratory system is responsible for gas exchange, while the excretory system is responsible for maintaining fluid balance. The immune system is responsible for destroying foreign pathogens.

There can be two classes of antigens on blood cells: one can distinguish ABO blood types and the second is the Rhesus factor (Rh factor), which determines positive or negative blood type.

A person with type O blood would not carry any antigens on their cells; however this individual’s plasma would contain anti-A and anti-B antibodies. Interestingly, this is why type O blood individuals are commonly known as universal donors, as their cells do not elicit immune responses from any other blood cell types. An individual with Rh^- would not carry the Rh factor antigen on the surface of their cells. Thus, O^-, correctly identifies the blood type of an individual lacking any of these antigens on their blood cells.

All of the given answer options are contained in blood at some point; however the main components are red blood cells (RBC’s), platelets, plasma, and white blood cells (WBC’s). Platelets are involved in coagulation, while white blood cells are involved in immunity. Plasma refers to the fluid matrix of the blood, and contains proteins, gases, amino acids, and hormones.

Hemoglobin is a specific protein located in red blood cells. Oxygen binds to hemoglobin for transport through the boold. Neither of these are considered major components of blood.