When is it appropriate to downshift an automatic transmission?

Answer: B — When going down grades

Downshifting an automatic transmission is especially appropriate when going down grades. This action helps to utilize engine braking, which reduces reliance on the brakes alone. By downshifting, the engine can help control the vehicle's speed, preventing the brakes from overheating and maintaining better control of the vehicle on downhill slopes. While accelerating may not typically require downshifting in an automatic, making a sharp turn generally does not necessitate downshifting either, as it can affect vehicle stability. Additionally, slowing down for a stop sign may involve reducing speed, but an automatic transmission is designed to manage gear shifts efficiently without the need for manual downshifting in most cases. This makes downshifting during descents the most beneficial and appropriate choice among the options provided.