指针式万用表测量电阻，使指针尽可能接近标度尺的几何中心。
参考答案：对
食品变质的原因有物理、化学、微生物三个因素。
Mr．Black must be worried about something． You can ________ it from the look on his face．[ ]
A．reason
B．recognize
C．read
D．realize
