Explanation/Reference:
Explanation:
It is not true that DES-EEE1 uses one key.
3DES can work in different modes, and the mode chosen dictates the number of keys used and what functions are carried out:
DES-EEE3 uses three different keys for encryption, and the data are encrypted, encrypted, encrypted.

DES-EDE3 uses three different keys for encryption, and the data are encrypted, decrypted, encrypted.

DES-EEE2 is the same as DES-EEE3, but uses only two keys, and the first and third encryption

processes use the same key.
DES-EDE2 is the same as DES-EDE3, but uses only two keys, and the first and third encryption

processes use the same key.
Incorrect Answers:
B: It is true that DES-EEE2 uses two keys.
C: It is true that DES-EEE3 uses three keys.
D: It is true that DES-EDE2 uses two keys.
References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 808