The Efficiency of a Heat Engine Is Defined as the Ratio

The efficiency of a heat engine is defined as the ratio of

A) the heat input at the high temperature to the heat output at the low temperature.
B) the heat output at the low temperature to the heat input at the high temperature.
C) the work it does to the heat input at the high temperature.
D) the work it does to the heat output at the low temperature.
E) the work it does to the difference between the heat input from the heat output.