Upvote:1
What do you mean by suspicion? They will obviously ask about your previous visa and trip.
As long as you have valid reasons and no mal-intent in staying back in the US, and can clearly explain what you were doing in the US, prior to your F1, you are going to be fine.
I know of friends who have gone for visit to US; check out universities, stay with family/ friends, tourism, some business/ work related trip. So, a following F1 should not be an issue.
As long as the connection and reasoning between your B1 trip + extension & your new F1 has sound reasoning you should have no issues.
Bottom line, as long as they do not perceive some kind of flight risk/ mal intent in your interview conversation you should be good.
PS: Additional note: Since, you did not state what you were doing during your B1 trip and whether you applied for F1 only to make another stay.. I am suspicious because you are not clear or afraid/ hiding something?
If you can't be clear in the head about the above or speak with conviction, you might arouse suspicion with the consular officer.