It's really easiest to answer this question if you can draw the graphs on a whiteboard. Most of the graphs you find in textbooks make the assumption that for prop aircraft fuel flow is proportional to power and for jet aircraft fuel flow is proportional to thrust. Of course neither assumption is quite correct and modern turbofans fall somewhere between the two assumptions.
If the candidate answers the question along the right lines, you can really test his understanding by asking him to explain how headwind / tailwind affects the best range speed, or how the range and endurance speeds are affected by weight.