Heat pumps do work on a refrigerant to reverse the normal flow of
a. electrical energy
b. potential energy
c. mechanical energy
d. thermal energy

The correct answer is "thermal energy".

Explanation:

Refrigeration: It is the process of rejecting heat from low temperature reservoir and then, transfer it to high temperature reservoir.

Here, the heat is taken from the colder body and reject it to hotter body. The sink is at the lower temperature. The source is at the higher temperature.

Thermal energy: It is the energy that comes from heat.

The difference between the heat engine and refrigeration is the operating temperature.

In heat engine, the heat is transferred from high temperature reservoir to the low temperature reservoir. Heat engine operates as a heat pump. It is just opposite of the refrigeration.

Therefore, heat pumps do work on a refrigerant to reverse the normal flow of thermal energy. The correct answer is (D).

  distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

  slope of a graph = change in value of y -axis / change in values of x -axis

  comparing both the equations

    change in value of y -axis = change in position

  change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.