Consider the following statements.
I. The canonical forms have no real existence.
II. The molecule does not exist for a certain fraction of time in one canonical form and for other fractions of time in other canonical forms.
III. There is no such equilibrium between the canonical forms as we have between tautomeric forms (keto and enol) in tautomerism.
IV. The molecule such as has a single structure which is the resonance hybrid of the canonical forms and which cannot such as be depicted by a single Lewis structure.
Which of the above statements are correct?

Many misconceptions are associated with resonance and the same need to be dispelled.
You should remember that
(i) The canonical forms have no real existence.
(ii) The molecule does not exist for a certain fraction of time in one canonical form and for other fractions of time in other canonical forms.
(iii) There is no such equilibrium between the canonical forms as we have between tautomeric forms (keto and enol ) in tautomerism

(iv) The molecule such as has a single structure which is the resonance hybrid of the canonical forms and which cannot such as be depicted by a single Lewis structure.