According to the report, men now spend________time preparing meals they did ten years ago. [ ]

A. twice more than the amount of  

B. more than twice the amount of

C. more than the twice amount of  

D. more than the amount of twice

对于碳素结构钢而言，公称容量比较小的炼钢炉冶炼的钢轧成的钢材，同一冶炼、浇注和脱氧方法、不同炉号、同一牌号的A级钢或B级钢，允许组成混合批，但每批各炉号含碳量之差不得大于（），含锰量之差不得大于（）。