They talked for about an hour of things and persons ________ they remembered in the school.

It’s unwise to ______ you understand something when you don’t.

He is tearing up what he has written ________and beginning over again[ ]

There is a limit________ the amount of pain we can bear.[ ]

In 1986, the Chinese government ________ a law stating that by the year 2000 every Chinese child would have nine years of compulsory education.