76.By raising questions and giving / listing sample answers.By asking and answering questions.
77.there are three types of liars.
78.Because it benefits the liar at the cost of other people’s interests.Because it benefits the liar but harms / does harm to other people.Because it harms / does harm to other people.
79.①speaking through one’s fingers ②putting one’s hands over one’s face ③playing with one’s hair or clothes ④being unable to stay still for any length of time（列举出以上任意三者即可）
80.How to tell if someone is lying