Expressing Certainty and Uncertainty

Accepting Expression:

- I’m certain.

- Of course

- I am sure.

- It is confirmed.

- No doubt about it.

Declining Expression:

- I’m not certain.

- I am not sure.

- I doubt about it.

- I don’t know

Example :

 1. Peter : Are you sure air pollution is more dangerous for the children?

     Jim     : Yes, I'm quite sure. It causes the illness for them.

2.  Anne : Are you sure all the garbage is easy to destroy?

    Marry : No, I doubt about it. The garbage like plastics is difficult to destroy