Which of the following is true regarding the use of thrust reversers during operations?

The statement that thrust reversers must be operable for landing is true because thrust reversers are vital for enhancing deceleration during the landing phase of aircraft operations. They assist in reducing the landing distance, particularly on shorter runways or in adverse weather conditions where stopping distance may be a concern. Having functional thrust reversers ensures that the aircraft can safely and effectively slow down after touchdown, making them a critical component for the landing process.

The other options suggest incorrect scenarios for thrust reverser functionality. Being inoperative under any circumstances ignores their importance during landing, where they are particularly beneficial. Additionally, the requirement for thrust reversers is not limited to takeoff; they can provide significant advantages during landing as well. The notion that thrust reversers should always be checked before taxiing emphasizes a pre-flight safety check, but it does not elucidate the critical necessity for them to be operable specifically during landing, which is a more crucial operational phase for controlled stopping. Thus, the correct answer highlights the essential role of thrust reversers in ensuring safe aircraft operations during the landing phase.