Not counterfeit, spurious, false, or adulterated
Belonging to, or proceeding from the original stock; native
Certain to act or be a specified way.
Physically secure and certain, non-failing, reliable.
Certain in one's knowledge or belief.
Yes, expressing noncommittal agreement or consent.
Yes; of course.
You're welcome; polite response to being thanked.
Without doubt, certainly.