The question is impossible to answer.
The efficiency of a heat engine depends on the temperatures of the hot and cold sides of the heat engine. The type of terrain does not influence a heat engine.
If the teacher wanted to know about the influences of altitude on efficiency, that might have been a more interesting question. High planes might higher than other hilly places.
Air is generally colder at altitude and gives jet engines an efficiency boost at altitude. But the fundamental physics reason is because of the difference in temperatures.