The interrogation, like a certain inflection in the voice, may indicate that a sentence, though declarative in form, is really a question and requires an answer.
You are, of course, familiar with New York?
THE EXCLAMATION The exclamation mark is the mark of strong emotion.
_Rules for the Use of the Exclamation_ 1.

After every expression of great surprise or emotion.
Look, my lord! it comes! Angels and ministers of grace defend us! Alas! my father.
2.

After interjections and other exclamatory words.
Hurrah! Good! Away! Oh! Where the exclamations are repeated without particularly emphasizing each one, each may be followed by a comma except the last.
Ha, ha, ha! That's a good joke! O used as a vocative or to express a desire or imprecation does not call for an exclamation.
O John.
Oh, yes.
O, that night would come! The exclamation is sometimes used in job printing to fill out a display line or for other inadequate reasons.

These uses should be avoided.
THE APOSTROPHE The apostrophe is primarily the sign of the possessive case, but it has several other uses.
_Rules for the Use of the Apostrophe_ 1.

The apostrophe for the possessive case is added only to nouns, not to the pronouns, which have their distinct possessive forms.