cryptography/security engineering

Suppose we are using AES in its CBC mode of operation. If a 1-bit error occurs in the communication (that is, if a single bit of the ciphertext is accidentally flipped), how many bits (not bytes or blocks) of the recovered message will be wrong on average? Recall: the block size of AES is 16 bytes ( 128 bits). Select one: a. 128 b. 64 c. 65 d. It depends on the key-length whether it is 118,192 or 256 bits. e. 256