单选题图所示为超静定桁架的基本结构及多余为知力X=1作用下的各杆内力，EA为常数，则为（　　）。<br/> <br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325564_0.jpg"><br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325564_0_1.png">