当两种不同材料的声阻抗相差多少时，就会产生界面发射（）。

A.0.1%

B.0.01%

C.0.02%

D.0.05%

E.1%

Drug use among teens concerns many people in California. Advocates of the "Stop Drugs Now" program, which was piloted in public schools in five California counties last year, argue that the program should be used throughout the state to decrease drug use among teenagers.
Which of the following statements, if true, would most strengthen the argument of the advocates of "Stop Drugs Now" that the program should be expanded statewide ？（）

A. School programs are far less important than parental messages in influencing a teenager’s decision to use drugs.

B. Drug use among teens in the five counties where the "Stop Drugs Now" program was piloted has been dropping steadily for over a decade.

C. Teenagers at the public schools where the "Stop Drugs Now" program was piloted reported higher average levels of drug use than did teenagers at private schools in the same counties where the program was not piloted.

D. There is evidence that teenagers who start smoking at an early age are more likely to experiment with illegal drugs than teenagers who do not smoke.

E. The percentage of teenagers who reported using drugs at the schools where the "Stop Drugs Now" program was piloted dropped more in the last year than in any other year over the last decade.