A manual for writers of research papers, theses, and dissertations, Ninth edition - Kate L. Turabian 2018

Question marks
Punctuation
Style

Put a question mark at the end of a complete sentence phrased as a question.

Who would lead the nation in its hour of need?

Put a question mark after a clause phrased as a question and included as part of a sentence. Do not use quotation marks unless the question is a quotation and the rest of the sentence is not.

Would the union agree? was the critical question.

If the included question is at the end of the sentence, do not add a period after the question mark. You are not required to capitalize the first word of the included question, but an initial capital helps readers identify the question, especially if it includes internal punctuation. If the sentence becomes awkward, you may instead rephrase the question as a declarative statement.

Several legislators raised the question, Can the fund be used in an emergency, or must it remain dedicated to its original purpose?

Several legislators raised the question of using the fund in an emergency, which was not its original purpose.

A question mark may also indicate doubt or uncertainty, as in a date.

The painter Niccolò dell’Abbate (1512?—71) assisted in the decorations at Fontainebleau.