— How long is it ___ the new math teacher came here?  

— wo weeks. The students just wonder how ___ they can go with him.[ ]

A. since, far    

B. when, soon      

C. before, far      

D. that, long

对库存书流转情况的分析，分出存书中的（）及待处理的比重，然后再反过来检验进货量。这就是库存结构控制。