Last year all refuse collected by Shelbyville city services was incinerated. This incineration generated a large quantity of residual ash. In order to reduce the amount of residual ash Shelbyville generates this year to half of last year's total, the city has revamped its collection program. This year city services will separate for recycling enough refuse to reduce the number of truckloads of refuse to be incinerated to half of last year's number. Which of the following is required for the revamped collection program to achieve its aim? ['The refuse incinerated this year will generate no more residual ash per truckload incinerated than did the refuse incinerated last year.', 'The total quantity of refuse collected by Shelbyville city services this year will be no greater than that collected last year.', 'This year, no materials that city services could separate for recycling will be incinerated.', 'Refuse collected by city services will contain a larger proportion of recyclable materials this year than it did last year.']