Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Problem:Passage: The highway above switches back and forth as it climbs up the steep hillside. The much gentler slope of the road makes it easier for vehicles to reach the top of the mountain. The highway is an example of an inclined plane. Answer: inclined plane
Solution:
A highway that switches back and forth as it climbs up a steep hillside, yeilding a much gentler slope, is an example of what simple machine?