21. It pays to take part in social works in order to know the outside world better.
　　22. Listening to music enables us to feel relaxed.
　　23. We should bring home to people the value of working hard.
　　24. Taking exercise is closely related to health.
　　25. The condition of our traffic leaves much to be desired.
　　26. …change the course of history…
　　…turn over a new leaf…
　　…shape the destiny of a nation…
　　…shape the world…
　　…break a new ground…
　　27. Smoking has a great influence on our health.
　　28. Pollution poses a great threat to our existence.
　　29. We shall do our utmost to change and reverse the current situation.
　　30. Time is more than money.