The Carnot cycle is the most efficient heat engine cycle because: (a) the entropy of the working fluid (gas) never changes. (b) it's the only heat...

The Carnot cycle is the most efficient heat engine cycle because:

(a) the entropy of the working fluid (gas) never changes.

(b) it's the only heat cycle for which energy is conserved.

(c) there is no waste heat emitted during a Carnot cycle.

(d) the work done by the working fluid during a Carnot cycle equals the heat input during

the cycle.

(e) the entropy of the universe (working gas and external environment) doesn't change during

any step of the Carnot cycle.