2.？ Only by planting a large number of trees and grass can soil erosion be prevented.
3.？ Only those who have the courage to devote themselves to science can climb the peak of science.
Every unit can only seek development by going to the old and welcoming the new.
Only by working hard can we get rid of being beaten.
6. The meaning of this poem is that only by standing high can you see far.
7. Brave and diligent people are not afraid of difficulties, and only cowards and lazy people avoid difficulties.
8. Only careful calculation can lead an orderly life.
9.？ Only when social order is stable can people live and work in peace and contentment.
10. Only selflessness can vindicate your words and deeds.
1 1.？ Only by force can we occupy our own territory, zaojv.com.
12. Only by studying hard can teenagers make a difference in the future.
13. Only when students understand each other can they do a good job of unity.
14.？ Only by establishing lofty aspirations can learning be motivated.
15.？ Birds can only fly with the help of buoyancy of air.