In the United States, it is important to be on time , or punctual , for an appointment ,

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 the difference while teaching a class in a Brazilian（巴西的） 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 10:30 A.M. Two students came after 11 A.M. Although all the students greeted the professor as they arrived, few apologized(道歉)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, respectively．He gave them an example and asked them how they would react, If they had a lunch appointment with a friend，the average American student defined lateness as 19 minutes after the agreed time，On the other hand．the average Brazilian student felt the friend was late after 33 minutes．
In an American university, students are expected to arrive at the appointed hour．In contrast, in Brazil，neither the teacher nor the students always arrive at the appointed hour．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．
36. The word‘punctual’most probably means    .
A．1eaving soon after class      B．ing early
C．arriving a few minutes late    D．being on time
37. Why did the professor study the Brazilian students’behavior?   
A．He felt puzzled at the students’ being late．  
B．He felt angry at the students' rudeness．
C．He wanted to make the students e on time later．
D．He wanted to collect data for one of his studies．
38.  It can be inferred from the professor’s study of lateness in the informal situation that    ．
A．American students will bee impatient if their friend is five minutes late
B．neither Brazilian nor American students like being late in social gatherings
C．being late in one culture may not be considered so in another culture
D．Brazilian students will not e thirty-three minutes after the agreed time
39.  From the last paragraph we know that in Brazil    .
A. it is important to arrive at the appointed time
B．it is rude to keep the professor staying after class
C．it is normal for students to leave during lectures
D．it is acceptable for professors to be late for class．  D