Which of the following is the correct statement of the second law of thermodynamics?

A. It is impossible to construct an engine working on a cyclic process, whose sole purpose is to convert heat energy into work.

B. It is impossible to transfer heat from a body at a lower temperature to a higher temperature, without the aid of an external source.

C. There is a definite amount of mechanical energy, which can be obtained from a given quantity of heat energy.

D. All of the above