How many bits can be used for keys in AES encryption?

In AES (Advanced Encryption Standard) encryption, the key sizes that can be utilized are specifically defined as 128 bits, 192 bits, and 256 bits. This range of key sizes is critical because it directly impacts the security level of the encrypted data; larger key sizes generally mean a more secure encryption scheme due to the exponentially increasing number of possible key combinations.

The 128-bit key is the minimum length used in AES, while the maximum is a 256-bit key, which stands as one of the strongest encryptions available for securing sensitive information. The availability of multiple key sizes allows for flexibility and scalability in security needs, enabling users to choose an appropriate level of protection depending on the sensitivity of their data.

The other options incorrectly list key sizes that do not conform to the established AES standards, either by including sizes that are not part of AES-defined key lengths or by providing combinations that include non-standard sizes. Therefore, option B stands as the correct answer, as it accurately reflects the key sizes supported by the AES encryption standard.