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.

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.