93. 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.

(A) the frequency of inventory turnovers can be

(B) the frequency of inventory turnovers is often

(C) the frequency with which the inventory turns over is often

(D) how frequently is the inventory turned over are often（E）

(E) how frequently the inventory turns over can be

Choice E, the best answer, grammatically and clearly makes the statement “x and y can be crucial,” in which x and y are parallel clauses, each introduced by the conjunction how. This parallelism is preferable to the use of the noun phrase the frequency in A, B, and C. Furthermore, the frequency of inventory turnovers in A and B is less clear than how frequently the inventory turns over. In B and C is often does not agree with the plural compound subject. Choice D ungrammatically reverses the subject-verb order with is the inventory.

og说的是讲求平行，然后一下就把abc排除了，我就纳了闷了，不是说短语优于从句么，而且逻辑上的平行也优于形势上的平行啊，A挺好的啊~~~~~郁闷~~~

同意楼主的看法，再补充一点：

the frequency of inventory turnovers 表达的是“inventory turnovers 的the frequency”是名词性短语，表达的是从属关系

而how frequently the inventory turns over则是说“the inventory turns over如何”表达的是一个完整的事情，有完整主谓（宾）结构。

好比说：I run quickly. 就不能表达为: the quickness of my running.