It was on the behest of the officer that he made those improvements.

Answer: Option B

Suggestion : an idea or plan put forward for consideration.
Orders : the arrangement or disposition of people or things in relation to each other according to a particular sequence, pattern, or method.
Recommendation : a suggestion or proposal as to the best course of action, especially one put forward by an authoritative body.
Request : an act of asking politely or formally for something.
Behest : a person's orders or command.

Synonym of Behest is Orders