Final answer:
The subject of this question is Engineering and it refers to the minimum dimension required for every landing.
Step-by-step explanation:
The subject of this question is Engineering. Specifically, it is referring to the minimum dimension that every landing should have.
In engineering and aviation, landings refer to the act of an aircraft touching the ground during takeoff or landing. The minimum dimension mentioned in the question is an important factor for safety and maneuvering purposes.
In this case, the answer to the question is 4 inches. This means that the minimum dimension of every landing measured in the direction of travel should be 4 inches.