单项选择题

A、Δ=(25–24.8)/(50-10)*100%=0.5%
B、Δ=(25–24.8)/50*100%=0.4%
C、Δ=(24.8–25)/(50-10)*100%=-0.5%
D、Δ=(24.8–25)/50*100%=-0.4%