2. Please select all the valid statements about the overall structure of the AES cipher:

a. An "Add Round Key" transformation is performed at the end of the Final Round.

b. An "Add Round Key" transformation is performed before the Round 1.

c. Every round of AES consists of four stages of transformation.

d. Its decryption and encryption procedures are identical.

e. Every stage of transformation in every round is reversible.

3. Please select all the valid statements about the AES key expansion procedure for the 128-bit key:

a. Ten 128-bit round keys will be derived for Round 1 to Round 10 transformations.

b. The original 128-bit key is directly used in an "Add Round Key" transformation performed before the Round 1.

c. Given the four consecutive words of the 10th round key, we cannot reversely derive the 9th round key.

d. The non-linearity property in key expansion is achieved by using the 10 round constants.