Expressing Certanty

When you are sure that something will or will not happen in the future, use this expressions, you may respond as follows:
or
Yes,
I am (absolutely / quite)
sure
certain
possitive
(he will)
Definitely.
Certainly.
Of course.
or
- It's confirmed
- No doubt
- One hundred percent sure.
  Here is an example of the use of the expressions in the conversation.
Tamrin: Hey, do not you know that we now have a school bus?
Word: Are you certain?
Tamrin: Yes, of course. The Headmaster himself told me.