I must do my homework well every day. Students must not smoke in a school. You must not use your phone while teaching a lesson. Pupils must wear a uniform in a high school. Students must throw litter in trash. You ought to learn English to learn abroad. You ought to greet teachers. You ought to pass the exam successfully to have a good mark. You have to do self-study to take the points. They have yo come in the class in time. I have to do my homework. We need to do overwork. We need to prepare for the exam. You need to learn English well. He doesn't to move fastly like this when many people go out by the door. Students need to respect teachers and each other. Students cannot come to class by the time of self-study. We can found new students' club. You can't come in the class if you late. Can we finish our class now? All students of the MUST could have passed TOEFL. Could you help me to do my homework? A teacher is late. She could have some trouble...