Final answer:
The commercial ground school hour requirements vary by aviation authority, with no set number of hours universally required. Each country's civil aviation authorities determine their own regulations for pilot ground school training.
Step-by-step explanation:
The commercial ground school hour requirements vary by aviation authority, which means the correct answer to the question would be 'd) Varies by aviation authority'. The requirements for ground school are established by individual countries' civil aviation authorities and can encompass topics such as aerodynamics, meteorology, airspace regulations, human factors, navigation, and more. Ground school is an essential part of pilot training, providing the theoretical knowledge necessary to safely operate aircraft.
For the Federal Aviation Administration (FAA) in the United States, for example, commercial pilots are required to complete certain ground school training or to have passed knowledge tests that cover the areas mentioned, but the FAA does not mandate a specific number of ground school hours. Every country's aviation authority might have varying requirements, and it's important to consult the regulations of the specific authority governing the airspace where one intends to operate.