A cryptanalyst intercepted a cipher that was composed entirely of Arabic numerals to convey military information to the enemy, and knew that each Arabic numeral in the password represented only one English letter. Which of the following is the least helpful in cracking this password? (). ['Know how often two letters appear together in English.', 'Know how often vowels appear in English.', 'Know that the frequency of odd numbers relative to even numbers in passwords is close to the frequency of R relative to E in English.', 'Know military-specific vocabulary in English.']