Questions (4): direct questions in academic writing
Do not ask direct questions in academic writing. By definition, the reader will not be able to answer you. So they are examples of the rhetorical question (q.v.). As that article says, you should avoid rhetorical questions in academic writing.
It is acceptable to say what question you are trying to answer: "This dissertation is trying to answer the question, 'What happened on that fateful day?'", or "Some opponents of this theory may ask 'What about the Law of Diminishing Returns?'" Here the question (note the question mark) is being quoted, not directly asked. (In grammatical terms, it is a Subordinate Clause, not the Main Clause. In the first example, it is in apposition to the noun 'question'; in the second, it is the Object of the verb 'ask'.)
It is also entirely acceptable to use indirect questions in academic writing.