Final answer:
The question is about aeronautics and specifically refers to the removal of tow-bar and bypass pin during pushback.
Step-by-step explanation:
In the context of aviation, the subject of this question is aeronautics. Aeronautics is the study and practice of designing, building, and operating aircraft. The terms 'tow-bar and bypass pin' indicate that the question is referring to aviation operations, specifically during pushback, which is the process of moving an aircraft backwards from the gate or parking position.