Fill in the text with correct choices

Usually, [that|when|which|what] our school day was going on, there was a great noise, [that|who|which|where] could be heard out in the street. The people passing by could hear pupils [who|when|what|which] were chanting in unison after the teacher, the tapping of the teachers' rulers on the tables and a lot more. But that day the atmosphere was still, and even the air, [who|what|where|that] usually blew in gusts, did not seem to stir. Through the window I saw my classmates [which|that|who|when] were already in the places, and our teacher was walking up and down with his terrible iron ruler, [which|that|who|when] he kept under his arm. I had nothing left to do but to open the door and to go to my desk in front of all the students [that|which|who|what] were already in their seats. The reason [that|why|what|when] I was surprised was that in the back I saw a person [who|what|when|whom] I had never seen before. The teacher, [that|which|who|when] sounded really friendly this time, told me to go to my place. I noticed that the teacher had his white shirt and tie on [which|what|when|who] he only wore on the day of inspection. The teacher mounted the chair, which was on the podium. His voice suddenly cracked [how|when|that|which] he began: "This is the last lesson that I am teaching you. The Ministry of Education does not allow me to teach any longer."