Which best describes why heat pumps are reversible? O They can heat and cool an indoor space.
O They involve a metal expanding or contracting against another.
They combust and can also add coolant.
They allow a piston to move up and down.

I would say the first one.

A: They can heat and cool an indoor space.

Explanation:

Reversible heat pumps are capable of providing both heating and cooling processes using the same two environments. When heating, they use the external pipes to absorb heat and release that heat into the indoor environment. When cooling, they absorb the heat from indoors and release that heat into the outside environment.

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.

force required to detach it is given by

charges are taken to be fundamental charge

now we have

so above is the minimum distance at which it will detach