Which of the following is an example of irony in macbeth?

Dramatic Irony is essentially anything we as readers know that the characters in the story do not.

One example of dramatic irony could be the case of Lady Macbeth's 'illness'. While the characters in the scene (ie. The doctor and the nurse) initially cannot figure out the true meaning behind her seemingly entranced rituals (excessive hand washing, for example), we as readers understand that it's because she is trying to wash her hands clean of King Duncan's blood.

You could also use the battle scene(s) as an example. We know Malcolm's battle strategies to ambush Macbeth while Macbeth knows nothing of it.

There are many examples in Act V that you could use, but these are only two examples.