During what phase of flight would you retract flaps?

The correct choice is during a go-around, which is a phase of flight in which a pilot decides to abort the landing and gain altitude to prepare for another approach. Retracting the flaps during a go-around is essential for increasing the aircraft's climb performance. The Cessna 172 has the capability to climb more effectively when the flaps are retracted, as it reduces drag and allows the airplane to achieve a higher rate of climb. This is critical because a go-around can occur in response to various factors such as an unstable approach or runway obstructions.

In contrast, during takeoff, flaps are typically extended to provide additional lift at lower speeds, and it is not immediately safe to retract them. When landing, flaps are fully extended to ensure proper descent and landing characteristics. In cruise, flaps are also retracted, but the context of the question specifically pertains to the actions taken during the go-around phase, making this the most appropriate scenario for flap retraction. Thus, the go-around is the critical moment when retracting flaps enhances the aircraft's performance and safety.