In the past the children were made ______15hours a day.

It is difficult for us to learn a lesson in life __________ we’ve actually had that lesson.

Everybody, men and women, old and young, _____ sports and games.

“Your homework is all right; , you can do it better, I think.” said the mother.

The smog arrived in the Yangtze River Delta region on Nov．30，_________the air quality in 1 2 cities out of 25 was rated as severely polluted by Dec．1．