In order for multicellular organisms to maintain homeostasis

A. their cells must continually grow in size.

B. their organ systems must work together.

C. their cells must all be identical.

D. each cell must act like an individual organism.

In order for multicellular organisms to maintain homeostasis B. their organ systems must work together. So the answer is letter B. This is because in order for the body to maintain hemostasis, it has to maintain the body temperaturw in any weather and climate it will experience.

I'd assume it's B, it makes the most sense. If cells acted alone, it probably wouldn't work out. If all cells were the same, you wouldn't really have an organism that would have to worry about homeostasis. If they all grew in size, there would be giant amoeba everywhere : D