.People have planted a great many trees in order to _____ wind and sand in the desert.
Do you think camping and climing is of much___to our health?
The sooner we students___to the new school, the better it will be___our studies.
What___wonderful world it would be if all countries in the world could live in___peace with one another.
30. The man that people think is a black sheep in the city will ____ imprisonment.
29. These wild flowers are so special that I would do ____ I can to save them.