Completethe following sentences by filling in each blank with an appropriate word orphrase from the box below. Change its form if necessary.

答案：

1. boost；2. make concerted efforts；3. eradicate；4. relies on；5. retain；6. trekking；7. lag behind；8. contribute to；9. give full rein to；10. elaborates on；11. fall into；12. proceed from；13. put forward；14. contend；15. set out