完形填空

　　The new principal decided that he’d better first take a secret 　　1　　 before doing something about Class 5A, which was the worst class in Hill Valley High School．He didn’t need to be informed 　　2　　 the class was, for 　　3　　 were leading the way．

　　The door was shut from inside．The lock it had was missing, 　　4　　 knocked off, just leaving a 　　5　　 for the principal．

　　Though the principal had 　　6　　 badly behaved classes before, what appeared through the 　　7　　 was till a shock for him．It was a scene that was 　　8　　 seen in action films．But he knew what to do．He 　　9　　 go into the classroom, take hold of the 　　10　　 boy and punished him．This would be an example to the others．

　　He took a deep breath and then 　　11　　 open the classroom door．He had been prepared for the scene that there should be a shock of 　　12　　, but few treated him as an important 　　13　　, and some even paid little attention to his existence．

　　“Silence! ” he shouted at the top of his voice．This time it was really 　　14　　．They stopped what they were doing and stared at him．Quickly he walked up to the 　　15　　 boy in the room, who he 　　16　　 had been playing an important part and also had been shouting at the others at the top of his voice．

　　He seized the boy by the ear and 　　17　　 him to the front of the class．

　　“I’m going to punish you as an example to the rest,” he said．“ Now go to my office and wait for me．”

　　Then he turned to the class and 　　18　　 them about how to behave in school．

　　To 　　19　　 his speech, he said, “Does anyone have any questions?”

　　One of the students put up her hand．“ Yes, sir．I have．When can you free my 　　20　　 back to continue his class?”