Spokesperson: Contrary to what some have claimed, our group' s "Clean City" campaign has been a rousing success. After all, the amount of trash on the city' s streets today is significantly lower than when the campaign began. Which one of the following is an assumption required by the spokesperson's argument? ['Those who claim that the campaign has not been a rousing success are unaware of the degree of the decline in the amount of trash since the campaign began.', "The amount of trash on the city's streets was not declining at the same rate or faster before the campaign began than it did during the campaign.", "The amount of trash on the city's streets has declined steadily throughout the course of the campaign.", "The campaign has been more successful in reducing the amount of trash on the city's streets than has any other campaign in the past."]