单选题图所示结构（E为常数），杆端弯矩（顺时针为正）正确的一组为（　　）。<br/> <br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325579_0.jpg"><br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/8325579_0_1.png">