Here is a list of features of a block cipher mode. Select all that apply to the CBC mode.

A$.$

The key provided to the block cipher varies according to the ciphertext.

B$.$

Ciphertext must fit into a multiple of the cipher's block size; it can't be an arbitrary number of bits.

C$.$

The mode uses both the block cipher algorithm and the XOR operation.

D$.$

The mode requires an initialization vector.

E$.$

The key provided to the block cipher varies according to the plaintext.

F$.$

The mode relies on block encryption; it does not use the block decryption operation even when decrypting data.