5. I've lost my science book. Have you seen it anywhere?

 我把我的理科书丢了,你在什么地方见过吗?

本句中使用的是现在完成时。现在完成时由助动词“have (has)”+动词过去分词构成,其肯定式、否定式、疑问式如下:

肯定式:I / We / You / They have seen it. 我/ 我们/ 你/ 你们/ 他们(它们、 她们)见过它。

     He / She has seen it. 他/ 她见过它。

否定式:I / We / You / They have not seen it. 我/ 我们/ 你/ 你们/ 他们(它们、 她们)没见过它。

     He / She has not seen it. 他/ 她没见过它。

疑问式:Have I / we / you / they seen it? 我/ 我们/ 你/ 你们/ 他们(它们、 她们)见过它吗?

     Has he / she seen it? 他/ 她见过它吗?

这个时态的基本特点是和现在有密切的联系,它所使用的场合是:

①.    到现在为止这段时间内业已发生的情况:

例如:How many classes have you had today?

    你今天(到现在为止)已经上了多少课了?

②.    某个动作虽然已发生,但其后果和影响与现在有关:

例如:Mike has already gone to the Great Wall.

    麦克已经去了长城。(到现在为止不在这儿)

  试比较:

 (1). Have you finished your homework?

    你完成回家作业了吗?(强调到现在为止有没有做好)

    When did you finish your homework?

    你什么时候完成回家作业的?(强调具体完成时间)

 (2). I have learned 3,000 words.

    我已经学了三千个单词了。(强调到现在为止学了多少)

    I learned 3,000 words.

    我(过去)学了三千个单词。(过去的一种情况,现在可能不止了)

  过去分词的构成:

  规则动词分为四类:

①.  原形+"ed"。

例如:work  worked  worked  visit  visited  visited

②.  字尾为“e”时,只需加“-d”。

例如:like  liked   liked    live   lived   lived

③.  字尾为“元音字母+y”时,保留“y”,直接加“ed”。

例如:play  played  played    stay   stayed   stayed

字尾为“辅音字母+y”时,将“y”改为“i”,再加“ed”。

例如:study  studied   studied   cry   cried   cried

④.  末尾只有一个辅音字母的重读闭音节时,将最后的辅音字母重复后再加“ed”。

例如:stop  stopped  stopped  drop   dropped   dropped

  附:不规则动词中比较有规则的有:

  ①. 三种形式都一样的有:

    hit    hit    hit,   hurt    hurt    hurt

    let    let   let,   read   read / red /   read / red /

    put   put   put,   cost    cost     cost

过去式与过去分词一样的有:

   win    won  won,  understand   understood   understood

   think   thought   thought,  tell   told      told   

    teach   taught   taught,  sweep    swept     swept

    stand   stood    stood,  spend   spent     spent

    smell smelt/smelled smelt/ smelled,sleep  slept      slept

    sit  sat  sat, shine   shined / shone    shined / shone

    send  sent   sent,    sell      sold      sold

    say   said    said,   meet      met      met

    mean  meant   meant,   make      made      made

    lose   lost     lost,   lend    lent      lent

    leave  left  left,  learn  learned/learnt  learned / learnt

    keep   kept    kept,   hold   held       held

    hear   heard   heard,  have / has   had       had

    hang  hanged / hung  hanged / hung, get    got      got

    find   found   found,   fight    fought     fought

    feel   felt    felt,    dig      dug      dug

    catch   caught    caught,  buy    bought     bought

    burn  burned/burnt  burned/burnt, build built      built

    bring   brought    brought,   

  原形与过去分词一样的有:

    come   came  come,    become    became    become

    run    ran    run,       

  副词“also,both,often,usually”等在句中的位置。

这些词通常在句中置于行为动词之前,系动词之后,情态动词之后,在现在完成时中,要放于“have / has”和过去分词之间。

例如:He is often late for school. 他上学经常迟到。

    He is usually careless in the exam. 他考试中通常很粗心。

    They have both been to London twice.

    他们俩都去过伦敦两次了。

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