14. The largest collection ever found in England was one of about 200,000 silver pennies, _____ over 600 years old.

　 A. all of which　　 B. all of them　　 C. all of that　　　 D. all of it

13. Good ads _____ on the radio or TV often use words _____ people attach positive meanings.

　 A. broadcasting, for which　 　　B. which are broadcast, for which

　 C. broadcasting, for which　　　 D. broadcast, to which

12. Dr. Franklin failed many times but he finally _____ to find a successful way to solve the problem.

　 A. broke off　　 B. broke up　　 C. broke through　　 D. broke down