What are the different parts of the muscle?

Which of these serves as a reference for comparison during a scientific investigation? a)outcome variable (dependent variable) b) test variable (independent variable) c)control group d)hypothesis

Aboy jumps into a cold swimming pool and his body tempature goes down hus muscles ,blood vessels

Rarefaction is used for which of the following? a. creating a representative sample b. studying how disease impacts populations c. rediscovering species thought to be instinct d. determining which sea creatures live in an area