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doubt; question; suspicion; dubiousness
彼の説明に疑問を感じたので質問した。
I felt doubtful about his explanation and asked a question.
疑問があれば遠慮なく聞いてください。
If you have any questions, please don't hesitate to ask.
この問題については疑問点が多すぎる。
There are too many questionable points about this problem.