How does the cardiovascular system the body get rid of waste? ?

Not the rectum but the kidneys. cardiovascular system involves the blood flow and the urination to get rid of wastes. as the body had damaged blood cells or worn down cells, it moves the cells through three processes. respiration, when the cells are obtaining oxygen, then perspiration, when the blood or oxygen is used during motion or sleep, the body will emit heat and eventually move to the final stage whish it felicitation, when the body gets rid of unwanted wastes like bacteria, salts and excess liquids, through urination, the rectum moves SOLID wastes like the skin of the foods you eat, carbohydrates, and proteins that your body cannot use anymore. so your answer is partially correct but it is through facilitation.  

Yes you are correct use the scientific method