9. Techniques to employ the energy of the sun are being developed.

　　A. convert

　　B. store

　　C. use

　　D. receive

　　10. Since the Great Depression， the United States government has protected farmers from damaging drops in grain prices.

　　A. slight

　　B. surprising

　　C. sudden

　　D. harmful

　　11. Cement was seldom used in building the Middle Ages.

　　A. crudely

　　B. rarely

　　C. originally

　　D. occasionally

　　12. Medicine depends on other fields for basic information， particularly some of their specialized branches.

　　A. conventionally

　　B. obviously

　　C. especially

　　D. inevitably

　　13. We were astonished to hear that their football team had won the champion.

　　A. amazed

　　B. amounted

　　C. amused

　　D. approached

　　14. There is an abundant supply of cheap labor in this country.

　　A. a steady

　　B. a plentiful

　　C. an extra

　　D. a stable

　　15. The most crucial problem any economic system faces is how to use its scarce resources.

　　A. puzzling

　　B. difficult

　　C. terrifying

　　D. urgent