经络的作用有______。
参考答案：联系内外，网络全身、运行气血，协调阴阳、抗御外邪，反映病候、传导感应，调整虚实
Questions 11 to 15 are based on the following interview.
A. Dressing styles throughout the world. B. Taking a journey to Sri Lanka in South Asia. C. Life of a native Sri Lankan now living in California. D. Traditional dress in the interviewee’s home country.
按照显示回声的方式进行分类，灰度调制型属于（）。
A.B型超声
B.多普勒超声
C.A型超声
D.M型超声
E.D型超声
