1、第二单元语法知识一 频度副词1. 频度副词的位置频度副词常放在be动词、助动词、情态动词之后，实义动词之前。如：He is often late for school.他经常上学迟到。I shall always remember my first day at school.我将永远记得我上学的第一天。I usually do some shopping with my parents on Sundays.我经常在星期天和我的父母一起去买东西。2. 常见的频率副词频度副词，通常放在行为动词之前，系动词be、助动词和情态动词之后。它们所表示的含义和频度各不相同。下面是常见的频率副词alway
2、s的频度为100%，表示动作重复、状态继续，中间没有间断，意为“总是”。例：The sun always rises in the east.太阳总是在东边升起。usually的频度为70%左右，意为“通常，平常”，较少例外。例：He usually goes to bed at ten oclock.他通常在十点钟上床睡觉。often的频度为50%左右，意为“时常，经常”，不如usually那么频繁，表示动作重复，中间有间断。very often语气比often重，常位于句首或句末。例：He is often late for school.他经常上学迟到。He doesnt go home
3、 very often.他不经常回家。sometimes的频度为20%左右，意为“有时”，表示动作偶尔发生。例：It is sometimes hot and sometimes cold.天气有时热有时冷。never的频度为0，意为“从来不，永不”。例：My parents are never late for work.我的父母上班从不迟到。hardly可作副词，意为“几乎不，几乎没有”。如：Words can hardly describe how excited we were.我们激动的心情难以形容。seldom可作副词，意为“很少，不常”。如：I seldom have lunch
4、 at home.我很少在家吃午饭。It seldom snows there.那里冬天很少下雪。3. 频率副词的提问对时间频率，如once a year, twice a week等提问，疑问词用How often。how often指每隔多久，主要用来对频率进行提问。如：-How often do you go to see a film?你多久去看一次电影？-I hardly ever go tosee a film.我几乎从不看电影。例子I go to schoolfive times a week.How often do you go to school? Students hav
5、e vacationstwice a year.How often do students have vacations?The Smiths go travellingevery other year.How often do the Smiths go travelling?注意：对具体次数，如once, twice, three times等提问，疑问词用How many times。I go to schoolfive timesa week.How many times do you go to school ina week? Students have vacationstwic
6、ea year.How many times do students have vacations ina year?4. 精确的频度副词，即用次数表达事情发生的频率例：We go to school five times a week.我们一周去学校五次。The magazine comes out once a month.这杂志一个月出版一次。二 一般现在时1. 定义：一般现在时表示经常性、习惯性、重复性发生的动作或存在的状态。一般现在时常常和频度副词always, usually, often, sometimes, never等连用。2. 动词形态：一般现在时的动词有动词原形和动词第
7、三人称单数形式（简称三单）。当主语为第三人称单数时，谓语动词也相应用三单形式。动词三单的变化规则如下表：3. 句型结构：a.当动词为be动词时b.当动词为实义动词时：4. 一般现在时的主要用法：表示经常发生的动作、存在的状态或日常习惯，常与every day，often，always，sometimes等时间状语连用。She gets up at six every day.她每天六点起床。表示主语的特征、性格、能力等。Tom studies very hard.Tom学习非常努力。表示客观事实或普遍真理。The sun rises in the east and sets in the we
8、st.太阳从东边升起西边落下。Actions speak louder than words.行动胜于言辞。 新闻标题或小说章节的题目。Bank Robbery: Robbers take $1, 000, 000.银行抢劫案：匪徒抢走一百万美元。三由连词although引导的让步状语从句although意为“虽然，然而，尽管”，是连词，引导让步状语从句，大部分情况下可以与though互换。although引导状语从句时，不能与but、however连用，但可与yet、still连用。如：Although many difficulties are still ahead, we are determined to overcome them.尽管我们前方有许多困难，但是我们已下定决心克服它们。