Explanation:

Time sharing systems allow multiple users to access a computer system simultaneously by sharing time on a central processor.

• An airplane ticket reservation system involves many users accessing the system at the same time, often over terminals or networks.

Let’s look at the other options:

• (A) Multiprogramming: Runs multiple programs at once, but not necessarily user-interactive.
• (B) Real-time programming: Used where responses are needed within strict time limits (e.g., embedded systems, flight control systems).
• (D) Batch programming: Processes data in batches without user interaction; not suitable for ticket booking which needs real-time user input.

Therefore, the most suitable answer is: (C) Time sharing.