What are the two types of tie down systems mentioned?

The correct choice identifies TD-1A and TD-1B as the two types of tie down systems referenced in aviation operations. These systems are primarily utilized to secure aircraft on a variety of surfaces and under different environmental conditions, ensuring stability and safety during ground operations. The TD-1A and TD-1B tie down systems provide specific configurations and anchor points designed to withstand wind loads and other forces that can affect the aircraft when it is stationary. Understanding these tie down systems and their appropriate applications is crucial for maintaining aircraft safety, especially when it comes to preventing accidental movement or damage during maintenance checks or adverse weather conditions.