They have no idea at all ________.
You can't imagine what great trouble they have __________ the problem __________.
The boy was criticized for forgetting __________ his textbooks to school.
Practice __________ English every day, and you will surely improve your spoken English.
—It is better for you to lose weight by taking exercise every morning. —I think your suggestion deserves __________.
—I'm sorry, but I didn't mean __________ out your secret. —But you know, letting out one's secret means __________ one's feelings.