He once remarked that "All happy families ________ one another, but each unhappy family is unhappy in its own way".

Now I see you want to_______ the position as you said just now. Could you please give me a brief _______ your intention?

Of all the books on the shelf,        is of any use for improving our practical skills of survival in the competitive world.

(2013·北京高考)________ the course very difficult, she decided to move to a lower level.

(2013·重庆部分学校高三联考)At the edge of the grass，there's a sign saying“________ the grass”．