Doctors have said that as many as 50 percent of patients don’t take medicine directed.A.

问题补充：

Doctors have said that as many as 50 percent of patients don’t take medicine directed.

A. like

B. so

C. which

D. as

答案：

A. like

B. so

C. which

D. as

解析：句中 take medicine as directed 相当于take medicine as they are directed,as引导方式状语从句。