A new survey shows that 54 percent of Americans do not take prescription medicines ________ though they are important to their health．

1. A.
   as they instruct
2. B.
   as were instructed
3. C.
   as to be instructed
4. D.
   as instructed

A new survey shows that 54 percent of Americans do not take prescription medicines____ 　　　 though they are important to their health.

A. as they instruct　　 B. as were instructed　 C. as to be instructed　 D. as instructed