Which one of the following options is the block cipher mode that uses an encryption method which has a feedback mechanism where each plaintext block is XORed with the previously encrypted block, and…

ECB (Electronic Codebook) mode encrypts each plaintext block independently with the same key and has no feedback mechanism, causing identical plaintext blocks to always produce identical ciphertext blocks.

DES (Data Encryption Standard) is the underlying block cipher algorithm itself, not an operational mode - it defines how a single 64-bit block is encrypted using a 56-bit key.

CBC mode chains each block to the previous one by XORing the current plaintext block with the immediately preceding ciphertext block, then encrypting the result with the block cipher key such as a DES key. This feedback dependency means that a change in any block propagates through all subsequent blocks, providing diffusion and preventing the pattern leakage seen in ECB mode. An initialization vector (IV) is used for the first block since no prior ciphertext exists.

3DES (Triple DES) is a key-strengthening algorithm that applies DES three times in sequence to each block and is not a block cipher mode of operation.