Final answer:
The subject of this question is Aviation, which falls under Social Studies. It pertains to the use of an aircraft for commercial purposes, such as carrying passengers for hire or providing flight instruction for hire.
Step-by-step explanation:
The subject of this question is Aviation, which falls under the broader topic of Social Studies. The question refers to the use of an aircraft for commercial purposes, such as carrying passengers for hire or providing flight instruction for hire. This topic is relevant to the study of the development of civil airline infrastructure, airline regulations, and the impact of deregulation on air travel.