Sentence Correction

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) how frequently the inventory turns over can be