基 础 过 关第 3 课时 Section A (Grammar Focus - 4c)单元语法精讲 课 堂 导 学课 堂 导 学☆1. be supposed to do sth.和 be expected to do sth.结构 (1)be supposed to do sth.=be expected to do sth.应该做某事。to 是不定式符号,不是介词,后应接动词原形。常用来表示劝告、建议、 告知义务或责任等,相当于 should。如: You are supposed/expected to ask the teacher if you want to leave the classroom. 如果你要离开教室,你应该问问老师。 注意:be expected to do sth.比 be supposed to do sth.的主观性更强。如: You're expected to do your duty. 你应该恪尽职责。 (2)在口语中,常用否定结构“be not supposed to do sth.”,意为“不允许做某事,不应该做某事”。相当于 shouldn't。如: You are not supposed to smoke on the bus. =You shouldn't smoke on the bus. 你不应该在公共汽车上吸烟。 (3)was/were supposed to do sth.相当于 should have done sth.,表示“(过去)本应该做某事而实际上并没有做”。如: I was supposed to arrive at 7:00, but I arrived at 8:00. 我应该 7 点钟到,却 8 点钟才到。 (4)suppose+that 从句,当变为否定句时,否定词应该前移。类似的词还有 think, believe 等。如: I don't suppose he will tell you about it. 我认为他不会告诉你这件事。 (5)suppose sb.to do sth.猜想某人做某事。如: I supposed him to stay at home. 我猜他待在家。 ☆2. It+be+ adj.+to do sth.句型 (1)It+be+ adj.+to do sth.意为“做某事是……的”,it 为形式主语,真正的主语是后面的动词不定式。如: I think it's important to sleep eight hours a night. 我认为每晚睡足 8 个小时很重要。 (2)表示“(对某人来说)做某事是……的”,用句型 It+be+ adj.+(for/of sb.+)to do sth.,其中 sb.为动词不定式的逻辑主语。其具体用法如下: It+be+ adj. +(for sb.+) to do sth. 此句型中的形容词为描述事物特征的词,如difficult, important, easy, hard, necessary, possible 等,是说明动词不定式的。 It+be+ adj. +(of sb.+) to do st...