According to Carnot's theorem as restated in the source, how does the efficiency of a Carnot engine compare with other heat engines operating between the same two reservoir temperatures?

1. Carnot's result singles out reversible cycles as the most efficient possible way to operate between two fixed temperatures. 2. It is stated that a Carnot engine has the greatest possible efficiency of any heat engine operating between those two temperatures. 3. It adds that all engines using only reversible processes share this same maximum efficiency when working between the same temperatures. 4. Real engines, which involve irreversible losses such as friction, cannot match this maximum, so option A has the comparison backward. 5. Efficiency is tied to reversibility and to the reservoir temperatures rather than to size, ruling out options C and D. _Source: OpenStax College Physics (CC BY 4.0), Ch 15 "Thermodynamics", section 15.4 Carnot's Perfect Heat Engine: The Second Law of Thermodynamics Restated_