如图所示阶梯杆ABC受拉力F作用,AB段的横截面积为A1,BC段的横截面积为A2,-|||-里 _(2)gt (A)_(1), 两段长度均为l,材料弹性模量为E,则此杆的最大伸长线应变εmax为 __D.-|||-A. dfrac (F)(E{A)_(1)}+dfrac (F)(E{A)_(2)} B. dfrac (F)(2E{A)_(1)}+dfrac (F)(2E{A)_(2)} F A A1 B A2 C F-|||-C. dfrac (F)(E{A)_(2)} D. dfrac (F)(E{A)_(1)} l l