Blood functions as part of the system and the system.

options:
circulatory; excretory
digestive; musculoskeletal
endocrine; respiratory
immune; reproductive

Answer;

circulatory; excretory

Explanation;Circulatory system is an organ system that is responsible for transport of nutrients to all the body tissues. Blood circulates and transports nutrient such as electrolytes, amino acids and oxygen, carbon dioxide, hormones, and blood cells to and from the body cells to provide nourishment.The excretory system is responsible for the removal of waste products such as urea, uric acid, and creatinine from the blood and passing it out of the body as urine.The blood carries the waste products to the kidneys where the wastes such as urea, uric acid among other material are removed from the body.