Final answer:
A perfectly efficient machine is one that converts all applied power into outputted force without any losses, meaning its efficiency would be 100%. The mechanical advantage refers to the ratio of output force to input force, a measure that is maximized in an ideal machine.
Step-by-step explanation:
A perfectly efficient machine converts all the power applied to it into outputted force. This means that the efficiency of such a machine would be 100%. The mechanical advantage (MA) comes into play when discussing simple machines like levers, gears, pulleys, wedges, and screws. These machines can amplify the force that is applied to them, allowing us to do the same amount of work with less input force. The ideal mechanical advantage refers to the mechanical advantage of an idealized machine that loses no energy to friction, such as an inclined plane where the only work done is input work, meaning effort force multiplied by the distance over which it is applied.
Complex machines combine two or more simple machines and can offer greater mechanical advantage and efficiency when compared to single simple machines. However, the answer to the student's question about a perfectly efficient machine focuses on its ability to convert all applied power (input work) into output work or force without losses. In this context, the ideal machine would be option (c), as it implies no energy is wasted, which is a hallmark of perfect efficiency.