Questions 11 to 15 are based on the following passage: ( 10 分 )In the United States, it is important to be on time, or punctual, for an appointment, a class, a meeting, etc. However, this may not be true in all countries. An American professor discovered this difference while teaching a class in a Brazilian university. The two-hour class was scheduled to begin at 10 a.m. and end at 12. On the first day, when the professor arrived on time, no one was in the classroom. Many students came after 10 a.m. Several arrived after 10:30 a.m. Two students came after 11 a.m. Although all the students greeted the professor as they arrived, few apologized for their lateness. Were these students being rude He decided to study the students’ behavior.The professor talked to American and Brazilian students about lateness in both an informal and a formal situation: at a lunch with a friend and in university calls, respectively. He gave them anexample and asked them how they would react. If they had a lunch appointment with a friend, the average American student showed clearly lateness as 19 minutes:after the agreed time. On the otherhand, the average Brazilian student would be 33 minutes late.In an American university, students are expected to arrive at the appointed hour. In contrast, inBrazil, neither the teacher nor the students always arrive at the appointed hour. Classes not onlybegin at the scheduled time in the United States, but also end at the scheduled time. In the Brazilianclass, only a few students left the class at 12:00; many remained past 12:30 to discuss the class andask more questions. Arriving late may not be very important in Brazil, neither is staying late.
From the last paragraph we know that in Brazil,（ ）。
A．it is acceptable for professors to be late for class
B．it is rude to keep a professor staying after class
C．it is important to arrive at the appointed time
D．it is Normal for students to leave during lectures