A : You know what ! we can use this plant a herbal medicine
B : Are you sure ?
A : Yes, I am. I read an article about it on the internet afew days ago.
C : Tamrin : Hey, don’t you know that we have a school bus now?
D : Firman : Are you certain?
C : Tamrin : Yes, of course. The headmaster himself told me.
E : I heard, our classroom will be renovated in the next view days.
F : Are you sure?
E : Well, I can’t tell you for sure. I think we should ask our teacher.