15.It is well known in the supermarket industry that how items are placed on shelves and the frequency of inventory turnovers can be crucial to profits.
1.the frequency of inventory turnovers can be
2.the frequency of inventory turnovers is often
3.the frequency with which the inventory turns over is often
4.how frequently is the inventory turned over are often
5.how frequently the inventory turns over can be
答案是E,无疑问
但是对OG关于D选项的解释有点疑惑:Is the inventoryis not parallel to items are placed
D选项的错误应该是在被动这一点吧?为什么要要求前后从句的语态也要一致呢?