问题 Which ... is required ...? 说明是问必要条件,用简单的数学和逻辑关系可以看出这题的答案 目标是:In order to reduce the amount of residue ash Shelbyville generates this year to half of last year's total 方法是:to reduce the number of truckloads of refuse to be incinerated to half of last year's number.
我们知道,total # of residue ash = # of truckloads × residue ash per truckload, 根据题目要求,total # of residue ash 要减至1/2,方法是# of truckloads 减至1/2,要保证等式成立,即1/2 = 1/2 ×residue ash per truckload 这里的residue ash per truckload必须要小于等于1,即D选项no more residue ash per truckload incinerated than did the refuse incinerated last year.而E选项在此提到的The total quantity of refuse 并非必要条件,所以选D 而E选项在此提到的The total quantity of refuse 并非必要条件,所以选D
[此贴子已经被作者于2007-6-28 0:53:45编辑过] |