All combination locks manufactured by the Gulzar Combination Lock Company have a combination that consists of four elements a one-digit number, a two-digit number, and two letters of the alphabet. Each combination conforms to the following rules. i. The one-digit number is the first element in the combination. ii. The two letters of the alphabet are not adjacent elements in the combination. iii. The two-digit number consists of two different numerals. iv. The two-digit number has no numerals in common with the one-digit number. Which of the following must always be true of a combination?