When should you use a question mark at the end of a sentence?

When should you use a question mark at the end of a sentence?

A question mark should be used at the end of a sentence when it is a direct question. This means that the sentence is asking for information or seeking clarification. The question mark indicates to the reader that the sentence is interrogative in nature. It is important to note that a question mark should not be used at the end of a sentence that is merely expressing doubt or uncertainty, as this would be considered a statement rather than a question.