1 Jenny____as an engineer_half a year.A has worked;since B works;since C worked;for D has worked;for2 Susan hasn’t written any postcards yet.I haven’t written them,either.(保持原句意思)Susan hasn’t written any postcards yet._

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1 Jenny______as an engineer_____half a year.A has worked;since B works;since C worked;for D has worked;for2 Susan hasn’t written any postcards yet.I haven’t written them,either.(保持原句意思)Susan hasn’t written any postcards yet._____ __
1 Jenny______as an engineer_____half a year.
A has worked;since B works;since C worked;for D has worked;for
2 Susan hasn’t written any postcards yet.I haven’t written them,either.(保持原句意思)
Susan hasn’t written any postcards yet._____ _____ I.答案Neither have
3How long has he _____there?
A left B been C gone D was

1 Jenny______as an engineer_____half a year.A has worked;since B works;since C worked;for D has worked;for2 Susan hasn’t written any postcards yet.I haven’t written them,either.(保持原句意思)Susan hasn’t written any postcards yet._____ __
1、work是连续动词,不是瞬间动词,可以表示工作了一段时间,have·······表示完成时,for后面跟时间表示一段时间
2、Neither have I和so do I不同在于前者用于否定,后者用于肯定,表示与前面的情况一样
3、how long提问时间,be there 表示状态,前面有have,所以用been

I don't konw

1. 与for引出时状连用，表示已经当工程师半年了
2。为了避免重复前面句子部分内容，否定句用either 或nor 引导倒装句
3。他已经到那多长时间了。 been 是be的过去分词

1、作为工程师已经工作了半年了。for 加一段时间并且用现在完成时
2、意思为我也没写postcard。首先为否定，not either =neither。否定词放在句首要用倒装，将动词提前have
3、用现在完成时必须是长期的动词，不能用瞬间性动词，left，go，排除。was就更不对了，has been是has done...

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第一题选D，表示已经工作了一年半，since后面加时间点，而for后面加时间段。
Neither have 因为neither表示否定的，have是因为主语是第一人称。
第三题选B因为been表示时间段，是个延续性动词，AC都是非延续性动词。

第一题，是现在完成时态，have done something for 一段时间，如果用since的话，Jenny has worked as an engineer since half a year ago
第二题，Neither是也没有的意思，像Neither，none等位于句首，后面要倒装，I have就变成have I
第三题，How long要跟可延续的动词，left，...

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第一题先看后面的half a year是一个过程词，而since后必须接一个时间点，所以CD里选，有因为是一个过程，所以不能选C，因为wokded指的是一个点
第二题是固定结构，平时多积累
第三题how long提问，所以是过程，不能选AC又因为有there,be there

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1，for+时间段；since+时间点；这些都一般用完成时态。题中half a year是时间段所以选D
2，这里Neither和either都是也不的意思，Neither have I 是neither的倒装用法：neither+谓语动词+主语。
3，这句话意思是：“他在这里多长时间了？”
此题考查的是现在完成时用法。have+动词过去分词，因此排除D（was是is的过去式并非过去分词）。how long 强调的是时间段，因此，此空需填延续性动词。而A C 都是短暂性动词，been是延续性动词。所以选B

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1 Jenny______as an engineer_____half a year.A has worked;since B works;since C worked;for D has worked;for2 Susan hasn’t written any postcards yet.I haven’t written them,either.(保持原句意思)Susan hasn’t written any postcards yet._____ __ an e-mail adddress 已知数列{An}中,A1=e,A2=e^2,且当x=e时,f(x)=1/2(An-an-1)x^2-(An+1-An)取得极值求证数列{An+1-An}是等比求证数列{An+1-An}是等比数列当Bn=An*LnAn时,求数列Bn的前n项和Sn 已知数列{an}中,a1=e(e为自然对数的底数)an+1=an-lnan(1)求证1 this is an e-mail对an e-mail提问把下列字母组成单词:1 a r e b 2 e h t e a n p i 3 e e an p h t i write an e-mail 是什么意思 Do you have an e an e-mail的音标 an e-book音标急! seng an e-mail是什么意思 an=2^n/(2^n+1),求证:a1*a2*a3*a4*a5*.*an>1/(2e) 连词成句 1 is,an,writing ,father ,e-mail,my 2 sh连词成句1 is,an,writing ,father ,e-mail,my2 she ,insects,is,counting 已知函数f（x）=ln（ [e^x-1]/x)且数列｛an｝满足a1=1,an+1=f(an)求证｛an｝单调递减且an>0 An increasing popuation is an e------ probem in many countries send an e-mail address的意思 I,sent,you,have,E-mail,an why not ____send an e mail