Based on the preceding section, the most logical thought here is thinking that מ is the preposition מִן that is attached to a word after dropping the nun.
If so, we can wonder whether we'll find בחינה in our dictionary.
The answer is yes: בְּחִינָה, a feminine noun that means examination, test, inquiry.
Do you know the basic בָּחַן, to examine, try, that appears in many places in the Bible though not in its basic form?
All together we have than examination, than test, than inquiry.