阅读理解 When students from other countries come to the United States, they are sometimes shocked at the informality in American college and university classes. For example, American professors do not dress up and they generally call their students by their first names. Students can speak out in class, without raising their hands. Students can drink coffee, tea, juice, or soft drink during class. Foreign students can usually get used to these differences easily. However, tow examples of American informality are very difficult for some to understand. First, American students call their teachers by their first names. Instead of calling a teacher Mr. Smith or Professor Johnson, they call them Tom or Barbara. In some countries, students are not allowed to do that. Second, American students sometimes criticize(批评) the ideas of their teacher. They might also give their teachers suggestions about changing something in the class. In many countries, students cannot openly criticize their teachers or classes. Thus, some foreign students feel shocked, embarrassed and uncomfortable in