Related Clues:

• Question of self-doubt
• It's asked for a reason
• Kid's repeated rejoinder
• Q1
• 'Explain, please'
• "How come?"
• Request for a green light
• 'Ple-e-ease?'
• Request often accompanied by 'please'
• ''Could you explain that?''
• "Is it allowed?"
• 'How -- Be Sure'
• 'Ple-e-e-ease?'
• Question unknown to a mathematician, say?
• 'Go ask your mother' elicitor