Dialogue 1Peter : Are you sure air pollution is more dangerous for the children?Jim : Yes, I'm quite sure. It causes the illness for them.Dialogue 2Anne : Are you sure all the garbage is easy to destroy?Marry : No, I doubt about it. The garbage like plastics is difficult to destroyDialogue 3Tamrin : Hey, don’t you know that we have a school bus now?Firman : Are you certain?Tamrin : Yes, of course. The headmaster himself told me.