Final answer:
In a 4-bit key space, each bit has two possibilities: 0 or 1. Therefore, there are 2^4 or 16 possible keys.
Step-by-step explanation:
The question pertains to the number of possible keys in a 4-bit key space. In the context of digital systems and cryptography, a key is a piece of information (or parameter) that determines the functional output of a cryptographic algorithm. For a 4-bit key space, each bit can be either 0 or 1, and there are two possibilities for every bit. Therefore, the total number of possible keys is 2 raised to the power of the number of bits.
Using the formula 2n, where n is the number of bits, we get 24 which equals 16. So, the correct answer is C. 16. This means there are 16 distinct keys that can be formed from a 4-bit key space. Each key would be a unique combination of 0s and 1s.