You design engines for an automotive plant. You know that the cars that roll off the assembly line have engines that operate between 325 C and room temperature, and are only 49% efficient at converting the chemical energy of the fuel into the work of moving the vehicle. To improve the efficiency, based solely on the 2nd Law of Thermo, you try to:

A. develop better lubrication for the moving parts of the engine.
B. design more efficient means of transmitting mechanical energy, e.g. reciprocating to rotary motion.
C. design an engine that doesn't "run so hot".
D. design an engine that "runs hotter".