“An object completely submerged in a fluid displaces its ovn volume of fluid". This is:

Archimedes' principle

Explanation:

An object completely submerged in a fluid displaces its own volume of fluid is postulate from the Archimedes' principle.

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.