（题文）(2015·陕西) ____________ the delayed flight will take off depends much on the weather.

Afraid that he might get his hands________, the monkey had the cat _______chestnuts out of the fire.

Was it when you were attending high school _________you first listened to pop music?

Mary is in a difficult situation ________ we should help her.

Great changes ______ in China in the past 20 years.[ ]