一般可用a，也可用the，要看语境和具体情况
ask a question 问一个问题
1.The pupil held up his hand to ask the teacher a question. 小学生举手向老师提了个问题。
2. ask a question 提问题
3. Might I ask a question 我是不是可以提个问题?
4. Could I ask a question? 我可以问个问题吗？
5. May I ask a question 我可以问一个问题吗？
6. Sir, may I ask a question? 老师，我可以发问吗？
7. "Ah... may I ask a question first?" “嗯……我可以先问个问题吗？”
ask the question 问这个问题
1.You may ask the question "Where has the lotus pond come from?"
你们也许会问：“那荷塘自何而生？”
2. can ask him the question. 我可以问他这个问题。
3. He is the fifth person to ask me the question. 他是第五个问我这个问题的人了。
4. The one who guesses the answer is entitled to ask the next question .
猜中答案的人有权问下一个问题。
5. Counsel ask the witness question about his bank account.
法律顾问或律师问证人有关他银行账户的问题。
6. Should I see her, I would ask her the question. 万一我见到她，我就问她这个问题。
7. About this book, the reader will probably ask the one truly fatal question: who cares?
对于这本书，读者多半要问那个实在要命的问题：谁会理睬它呢？
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