Please Help

Conservation of energy

a principle stating that energy cannot be created or destroyed, but can be altered from one form to another.

Explanation:

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

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.