请阅读Passage 2,完成第1-5小题。

Passage 2

  Rewards and punishmenLs are used in different ways by different communilies to maintain social order and preserve cultural values. In all cultures,parents must teach their children to avoid danger and to observe the community's moral precepts. Adults also condition each other's observance of social norms,using methods ranging; from mild forms of censure,such aslooking away when someone makea an inappropriate remark,to imprisoning or executing individuals for behavior considered deviant or dangerous. The caning of American teenager Michael Fay in Sirigapore for vandalism in 1994 brought wide media attention to cultural differences in the application of punishment. Faced with increasing violence at home,many Americans endorsed Singapore's use of corporal punishment to maintain social order. Was Fay's punishment effective?  Whether he subsequcntly avoids vandalism is unknown,but the punishment did apparently lead to his avoidanc.e of Singapore-which he left promptly.                                                            

  The operant techniques societies use to maintain social control vary in part with the dangers and threats that confront them. The Gusii of Kenya,with a history of tribal warfare,face threats not only from outsiders but also from natural forces,including wild animals. Gusii parents tend to rely more on punishment and fear than on rewards in conditioning appropriate social behavior in their children. Caning,food deprivation,and withdrawing shelter and protection are common forms of punishment.

  In contrast,the Mixtecans of Juxtlahuaca,Mexico,are a highly cohesive c:ommunity,with little in temal conflict,and social norms that encourage cooperation. Their social patterns appeur adaptive,for the Mixtecans are dominated by the nearby Spanish Mexicans,who c:ontrol the official goverriment and many economic resources in their region. The Mixtecans do not generally impose fines or jail sentences or use physical punishment to deter aggression in either adults or children. Rather,they tend to rely on soothing persuasion. Social ostracism is the most feared punishment,and social ties within the commu- nity are very strong,so responses that reinforce these ties are effective in maintaining social order.

  In the United States,fear of social ostracism or qtigma was once a more powerful force in maintaining control  over antisocial behavior,especially in small communities. Today,even imprisonment does not appear to be an adequate deterrent to many forms of crime,especially violent crime. Although one reason is the inconsistent application of punishment,another may be the fact that imprisonment no longer carries the intense stigma it once bad,so that prison is no longer as an effective punishment.

根据题目要求完成下列任务，用中文作答。

教学片段：

老师：同学们好，今天我们要讲解新的语法项目——现在完成时。所谓现在完成时，顾名思义就是到目前为止已经完成，也就是说现在完成时用于表示到目前为止已经完成的行为。

比如：

I have already finished my homework.

大家可以看出，现在完成时是由“have+过去分词”构成，…，

接下来教师开始讲解现在完成时的各种用法。

以上片段选自某课堂实录，请分析该教学片段并回答下列问题：