Since empathy is essential for people to be willing to follow moral codes that sometimes require them to ignore their own welfare to help others, civilized society could not exist without empathy. Which one of the following is an assumption required by the argument? ['If everyone in a society is sometimes willing to ignore his or her own welfare to help others, that society will be civilized.', 'People who feel empathy tend to ignore their own welfare for the sake of others.', 'Civilized society can exist only if there are people who are willing to at least sometimes ignore their own welfare to help others.', 'Moral codes that include the requirement that people disregard their own welfare in order to help others have arisen within some civilized societies.']