NSA took the 128-bit algorithm Lucifer that IBM developed, reduced the key size to 64 bits and with that developed DES.
The following answers are incorrect:
Twofish. This is incorrect because Twofish is related to Blowfish as a possible replacement for DES. Skipjack. This is incorrect, Skipjack was developed after DES by the NSA . Brooks-Aldeman. This is incorrect because this is a distractor, no algorithm exists with this name.