单选题如图所示的刚架，各杆EI相同，C点竖向位移（向下为正）等于（　　）。<br/> <br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325546_0.jpg"><br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325546_0_1.png">