When the Availability of a rule is set to Withdrawn, the rule is removed from the list of rule candidates, as well as all other rule candidates that match the same:
Apply to class
Ruleset name, and Major version number
Based on this statement from the course. Row 1 and 2 would be removed as Row 1 is withdrawn and they both have the same Applies to class and Major RuleSet version. Likewise Row 3 and 4 would be removed as well based upon the same logic. You are correct that 5 is not chosen as it is not in the ruleset list. Leaving us with row 6.