4

　　The water companies were_instructed_not_to expose people to polluted water any more.自来水公司也接到命令，不能再让人们接触被污染的水了。(回归课本)

　　用法点拨

　　She instructed me in the use of the telephone.

　　她教我使用电话。

　　Those boys were instructed to wait there.

　　那些男孩被通知在那儿等。

　　Our teacher instructed that we (should) hand in our papers after class.

　　老师命令我们下课后把试卷交上。

　　归纳拓展

　　instruction n．教授；指导；(复数)用法说明，操作指南

　　instructive adj.指示性的，有教育意义的

　　instructor n．辅导员，讲师

　　be instructed to do sth.被指示做某事

　　instruct＋that从句，从句用should＋do形式，should可以省略

　　完成句子

　　(1)When I came in，he was instructing his son how_to_repair_a_car(如何修汽车)．

　　(2)The teacher instructed_the_students_to_start_off(命令学生出发)．

　　(3)You must read_the_instructions(阅读说明书)before you use it.

　　5

　　But he became inspired when he thought about helping ordinary people exposed to cholera.但当他一想到要帮助(那些)受到霍乱威胁的普通百姓时，他就感到振奋。(回归课本)

　　用法点拨

　　Don't expose it to the sun.不要把它暴露在阳光下。

　　The film has been exposed.这个胶卷曝光了。

　　The magazine exposed the politician as a crook.

　　这本杂志揭露这位政治家是一个骗子。

　　归纳拓展

　　be exposed to使暴露在......

　　expose sb./sth. to...使......暴露在......

　　expose sth.揭露某事

　　exposure n．暴露，揭露

　　overexpose v．使(胶片等)曝光过度；对......报道过频

　　完成句子

　　(1)He_exposed_the_plan(他透露了这个计划)to the newspapers.

　　(2)Keep indoors and don't_expose_your_skin_to_the_sun(不要让皮肤暴露在太阳下)．

　　(3)The photograph is too light：it must have_been_overexposed(曝光过度)．

　　6

draw a conclusion得出结论(回归课本)