How many unique transponder codes can be produced using "squawk" codes?

The correct choice reflects an understanding of how transponder codes, or "squawk" codes, are structured in aviation. Each squawk code is represented by a 4-digit octal number, which means each digit can take on any value from 0 to 7.

In octal notation, a digit has 8 possible values. Therefore, for a 4-digit octal number, the total number of unique combinations can be calculated as follows:

8 (values for the first digit) x 8 (values for the second digit) x 8 (values for the third digit) x 8 (values for the fourth digit), or 8^4. This results in 8^4 = 4096 unique squawk codes.

Understanding this system is crucial for pilots and air traffic controllers, as squawk codes are used for radar identification and help differentiate aircraft within controlled airspace. The other options represent calculations based on different assumptions or incorrect bases, which do not apply to the octal system used for squawk codes.