It is well know in the supermarket industry that how items are placed on shelves and the frequency of inventory turnovers can be crucial to profits.

D) how frequently is the inventory turned over are often
E) how frequently the inventory turns over can be


My choice was D. The OG answer is E. My questions is: Isnt “how items are placed” parallel to “how frequently is the inventory turned over” ? According to OG, the two statements are not. I am not convinced.

1.Can you please give your insight as to why they are not parallel?

Nope, D is not parallel

"how items are placed"
"how noun verb"

"how frequently is the inventory"
"how frequently verb noun"

"how frequently the inventory turns"
"how frequently noun verb"

I need the noun first and then the verb. (Frequently isn't a noun, if that's what was confusing you. It's an adverb.)