当用指针式万用表进行电阻测量时，为了提高测试精度，指针所指示被测电阻之值，应尽可能指示在刻度的中间一段，即全刻度的20％～80％弧度范围内。（）

A. chronic pain
B. brain chemical
C. nerve receptors
D. a clear definition
E. damaged nerves
F. painkilling therapies
G. an emotional response

Study on animals may finally discover some new ______ for human beings.