大学英语四六级语法知识

　　在大学中，单独考察的题型几乎是没有的，但是英语四六级语法知识点却贯穿整张试卷，下面小编为大家整理了基础语法知识，希望可以为大家带来帮助，一起来学习一下吧。
　　英语知识：用于现在完成时的句型
　　1)It is the first / second time…. that…结构中的从句部分，用现在完成时。 It is the first time that I have visited the city. It was the third time that the boy had been late. 2)This is the… that…结构，that 从句要用现在完成时. This is the best film that I've (ever) seen. 这是我看过的很好的电影。 This is the first time (that) I've heard him sing.这是我首次听他唱歌。
　　典型例题
　　(1) ---Do you know our town at all? ---No, this is the first time I ___ here. A. was B. have been C. came D. am coming 答案B. This is the first time 后面所加从句应为现在完成时，故选B。
　　(2) ---Have you ____ been to our town before? ---No, it's the first time I ___ here. A. even, come B. even, have comeC. ever, come D. ever, have come 答案D. ever意为曾经或无论何时，反意词为never，此两词常用于完成时。 This is the largest fish I have ever seen. It is / was the first time that-clause 的句型中，从句要用完成时。 注意：非延续性动词的否定形式可以与表示延续时间的状语连用。即动作不发生的状态是可以持续的。 (错)I have received his letter for a month. (对)I haven't received his letter for almost a month.
　　英语知识：现在进行时 现在进行时的基本用法：
　　a. 表示现在( 指说话人说话时) 正在发生的事情。 We are waiting for you.
　　b. 习惯进行：表示长期的或重复性的动作，说话时动作未必正在进行。 Mr. Green is writing another novel. (说话时并未在写，只处于写作的状态。) She is learning piano under Mr. Smith.

　　c. 表示渐变的动词有：get, grow, become, turn, run, go, begin等。 The leaves are turning red. It's getting warmer and warmer.
　　d. 与always, constantly, forever 等词连用，表示反复发生的动作或持续存在的状态，往往带有说话人的主观色彩。 You are always changing your mind. 典型例题 My dictionary ___, I have looked for it everywhere but still___ it. A. has lost, don't find B. is missing, don't findC. has lost, haven't found D. is missing, haven't found.
　　答案D. 前句是一个仍在持续的状态，应用进行时，由于没有找到，其影响仍然存在，应用完成时，瞬间动词用于否定式时可用于完成时。