单项选择题

若钢尺的尺长方程式为:L=30m+0.008m+1.2×10-5×30×(t-20℃)m,则用其在26.8℃的条件下丈量一个整尺段的距离时,其温度改正值为()

A.–2.45mm
B.+2.45mm
C.–1.45mm
D.+1.45mm