Read the following article and select the best answer. Article: A good teacher is many things to many people. In my own experience, the people I respect the most and think about the most are the teachers who demanded the most discipline from their students. I miss one teacher in particular that I had in high school. I think she was a good teacher because she was a very strict person. I remember very vividly a sign over her classroom door. It was a simple sign that said, "Laboratory--in this room the first five letters of the word was emphasized , not the last seven." In other words, I guess, labor for her was more important than oratory, which means making speeches. She prepared her work very carefully and demanded us to do the same. We got lots of homework from her. Once she had broken her arm, and everybody in the class thought that maybe the homework load would be reduced, but it continued just the same. She checked our work by stamping her name at the bottom of the papers to show that she had read them. I think sometimes teachers who demand the most are liked the least. But as time goes by, this discipline really seems to benefit the students. Question: The teacher put up the sign over her classroom door _ . - to remind the students that this room was a laboratory - to advise the students to follow the disciplines - to warn the students not to be careless - to tell the students to work hard in the classroom
The answer to this question is:
to tell the students to work hard in the classroom