According to FAA 8083-30, Chapter 11, what is considered the "big three" in airworthiness regulations?

The correct identification of the "big three" in airworthiness regulations according to FAA 8083-30, Chapter 11, refers to the essential parts of the Federal Aviation Regulations (FAR) that establish the standards for the airworthiness of aircraft and their components.

Part 21 covers the certification procedures for products and parts, ensuring that all necessary processes and requirements are met before an aircraft can be deemed airworthy. Part 43 outlines the maintenance, preventive maintenance, rebuilding, and alteration of aircraft, setting standards for ongoing airworthiness through proper upkeep and repair. Lastly, Part 91 details general operating and flight rules, providing comprehensive guidelines on how aircraft should be operated to maintain safety and airworthiness during flight operations.

These three parts work together to create a robust framework that ensures aircraft are safely designed, maintained, and operated, which is why they are commonly referred to as the "big three" regulations in the context of airworthiness.

The other choices refer to various parts of the FAR that focus on specific topics but do not represent the overarching structure necessary for ensuring the airworthiness of aircraft as effectively as the combination found in the correct answer.