The question mark ends a sentence that asks something. It shows that a sentence is a question. Since question marks can be used in a variety of ways, they have a few rules you must memorize.
Rule 1: Use a question mark after a sentence that asks a direct question.
Where should we go if it rains?
2: Use a question mark if a sentence starts with a statement but has a question at its end.
Charlie is coming to the party, isn’t he?
[This sentence begins as a statement, but ends in a question.]
Rule 3: If a question has an abbreviation at its end, include a question mark after the period.
Did you go to North Cedar St.?
[Abbreviation at the end of a question – add a question mark after period.]