Which letters are used in the hexadecimal number system?

The hexadecimal number system is a base-16 system that is widely used in computer science and digital electronics. It includes the digits from 0 to 9 and the letters A to F, which represent the decimal values 10 to 15. Therefore, the letters A, B, C, D, E, and F are integral to this system, as they extend the traditional numeric range of 0 through 9 to provide additional values needed for base-16 calculations.

The other options consist of completely unrelated letters that do not have any relevance in the hexadecimal system. Consequently, they do not contribute to the representation of values in this numeric system. Recognizing the importance of the digits and letters in hexadecimal is crucial for understanding computing concepts, especially when dealing with memory addresses and color codes in web design.