Answer :
Answer:
D
Explanation:
In multicellular organisms, the body is a system of multiple, interacting subsystems. Subsystems are groups of cells that work together to form tissues. Interactions are limited to the circulatory, excretory, digestive, respiratory, muscular, and nervous systems.
D all of the above. I know for sure organ systems and tissues are subsystems. Since subsystems are made up of cells I would include that as well.