Have you ever heard the theme song of the 29th Olympic Games, Hand in Hand, _____ in Chinese? [ ]

A. sing

B. to sing

C. singing

D. sung

假设某项检测项目的测定值在正常人群中呈正态分布，以均值±2S作为正常参考范围的上、下限，这时正常人出现异常结果的概率是多少（）

A.0.27%

B.0.5%

C.1.0%

D.2.5%

E.5%