Passage FiveIn the United States, it is important to be on time, or punctual, for an appointment, a class, etc. However, this may not be true in all countries. An American professor discovered this difference while teaching a class in a Brazilian (巴西的) university. The two-hour class was scheduled' to begin at 10 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 the scheduled time. Several arrived half an hour later. 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 a university class. He found that if they had a lunch appointment with a friend, the average American student defined lateness as 19 minutes after the agreed time. However, the average Brazilian student felt the friend was late after 33 minutes.In an American university, classes not only begin at the scheduled time in the United States, but also end at the scheduled time. In the Brazilian class, only a few students left the class at 12: 00; many remained past 12: 30 to discuss the class and ask more questions. While arriving late may not be very important in Brazil, neither is staying late.51. The word "punctual' most probably means______.