单选题设各杆的EA值相同，在图所示的桁架中，节点C的竖向位移为（　　）。<br/> <br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325550_0.jpg"><br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325550_0_1.png">