Cheryl knows that the OpenSSL password file protects passwords by using 1,000 rounds of MD5 hashing to help protect password information. What is this technique called?

Key stretching is used to improve weak keys. One way of implementing it is by repeatedly using a hash function or a block cipher, increasing the effort that an attacker would need to exert to attack the resulting hashed or encrypted data. The rest of the options were made up.