1._______ you return those books to the library immediately,
1._______ you return those books to the library immediately,you will have to pay a fine.
a.Until b.Unless c.If d.Provided
2.When you worry you can’t sleep and when you can’t sleep you worry ____.
a.much more b.even more c.many more d.few more
3.The river was high because it _____ for several weeks.
a.had been raining b.was raining c.has been raining d.rained
请选择并讲讲为什么.