All societies recognize certain rules to be so crucial that they define those rules as duties, such as rules restricting violence and those requiring the keeping of agreements. Contained in the notion of a duty is the idea that its fulfillment is so fundamental to a properly functioning society that persons obligated by it cannot be excused on the ground that its fulfillment would be harmful to their self-interest. This shows that __. Which one of the following most reasonably completes the argument? ['all societies overrate the benefits of certain rules, such as those governing the keeping of agreements', 'all societies recognize the possibility of clashes between individual self-interest and the performance of duty', 'societies have no right to expect people always to perform their duties', 'all societies have certain rules that no people are capable of following']