It is important to have your eyes examined regularly to check for any sign of eye disease that may not

have any ________. [ ]

A. symptom    

B. similarity      

C. sample      

D. shadow

不及格结果的类型不包括（）

A.书写误差

B.方法学问题

C.技术问题

D.室间质评物问题

E.不按时上报结果