Answer: The correct option is (At least one member must benefit in a symbiotic relationship.)
Explanation:
a scientific model is a model used to test theories. sometimes scientist use rats as a scientific model
Answer: it's because they need to provide a lot of energy.
Explanation: fat cells have many mitochondria because they store a lot of energy. Muscle cells have many mitochondria, which allows them to respond quickly to the need for doing work.
