He had to leave suddenly to answer/obey the call of nature.他只得匆匆离开去解决一下内急。I'm afraid I have to answer a call of nature.抱歉我要去趟洗手间。I felt the call of nature and so I stumbled down the external staircase to the evil-smelling loo.我感到内急，于是就踉踉跄跄地从外面的楼梯跑到臭气熏天的厕所。