【单选题】
某钢尺的尺长方程式为:L=30-0.003+1.25×10<sup>-5</sup>×30×(t-20℃),若用其在4℃的温度下丈量了60米,则其温度改正数和实际长度分别为()
A、-0.012m ;59.988m
B、+0.012m ;60.012m
C、–0.012m ;59.982m
D、+0.012m ;59.982m
A、-0.012m ;59.988m
B、+0.012m ;60.012m
C、–0.012m ;59.982m
D、+0.012m ;59.982m