Students shouldn’t be given so difficult a problem ______they can not work out.

________ nobody gave him any help, he must have done the research on his own.

The old man came to our restaurant so ____ that all of us were familiar with him [ ]

ver there—there’ s a very long, winding path_________ up to the house.

(2013·北京，30)I took my driving license with me on holiday，________I wanted to hire a car.