单选题图示刚架在荷载作用下，哪种弯矩图是不可能出现的？（　　）<br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251122/18930621_0.jpg"><br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251122/18930621_0_1.jpg">