Based on law of conservation of energy, how can we reasonably improve a machines ability to do work?

Based on the law of conservation of energy, how can we reasonably improve a machine's ability to do work? Move the machine to a different gravitational field. Increase the friction between its moving parts. Reduce the friction between its moving parts. We can reasonably improve a machines ability to do work by reducing the friction between the moving parts of machine. The correct answer is C. Gobble down five bananas and you'll have enough energy to swim for about an hour. That's because your body is a complex machine capable of turning one kind of energy (food) into another kind (movement). Cars can pull off the same trick. Depending on which make and model you own, you probably know that it does so many kilometers or miles to the gallon; in other words, using a certain amount of energy-rich gasoline, it can transport you (and a moderate load) a certain distance down the road. What we have here are two examples of machines—the human body and the automobile—that obey one of the most important laws of physics: the conservation of energy. Written in its simplest form, it says that you can't create or destroy energy, but you can convert it from one form into another. Pretty much everything that happens in the universe obeys this fundamental law. But why, and what use is it anyway? Let's take a closer look!

The correct answer is b