Extracting Administrator Passwords Using L0phtCrack

What are the alternatives to crack administrator passwords?
          There are quick, common, and string passwords audits. Quick checks only for dictionary words, common checks for dictionary words and common variations, and strong initiates a quick password audit followed by a common password audit and finally a brute force attack.

Why is the Brute Force attack used in the L0phtCrack tool?
          Brute force attacks are used because the are guaranteed to work at some point no matter how long it takes.