英语时态请教,麻烦你了,具体如下：At last firemen have put out a big forest fire in California.Since then they have been trying to find out how the fire began.Forest fires are often caused by broken glass or by cigarette ends which peopl

英语时态请教,麻烦你了,具体如下：At last firemen have put out a big forest fire in California.Since then they have been trying to find out how the fire began.Forest fires are often caused by broken glass or by cigarette ends which peopl
英语时态请教,麻烦你了,具体如下：
At last firemen have put out a big forest fire in California.Since then they have been trying to find out how the fire began.Forest fires are often caused by broken glass or by cigarette ends which people carelessly throw away.Yesterday,the firemen examined the ground carefully,but were not able to find any broken glass.They were also quite sure that a cigarette end did not start the fire.This morning,however,a fireman accidentally discovered the cause.He noticed the remains of a snake which was wound round the electric wires of a 16000-volt power line.In this way,he was able to slove the mystrey.The explaination was simple but very unusual.A bird had snatched up the snake from the ground and then dropped it on to the wires.The snake then wound itself round the wires.As it did so,it sent sparks down to the ground and these immediately started a fire.
上面这篇文章取自新概念二册第53课,请问文章中为什么前面部分为什么要用现在完成时,明显根据文章得知,火在后面提到的检查地面,找到电线上的蛇这些事之前就扑灭了,检查地面,发现蛇这些事都用过去时,火在这之前就扑灭了,扑火为什么不用过去完成时呢,按规则来讲应该用过去完成时和过去完成进行时啊,如果说是因为要强调对现在的影响,那就能视时态不顾了吗,那不就可以乱用了吗.另外,单看文章前两句中,since then 从那时起,都说了从那时起,前面扑火肯定是过去,为什么前面还用现在完成时,

英语时态请教,麻烦你了,具体如下：At last firemen have put out a big forest fire in California.Since then they have been trying to find out how the fire began.Forest fires are often caused by broken glass or by cigarette ends which peopl
问题1：“请问文章中为什么前面部分为什么要用现在完成时”
回答1：强调对现在的影响,可理解为“现在没事儿了”.如果你非要较真,那么请注意开头有个“At last”.这个虽然不是什么时态的标志性时间点,但是根据这个词我知道,作者是想说“很不容易啊这个火终于灭了,现在没事儿了”.是这个意思.
问题2：“扑火为什么不用过去完成时呢,按规则来讲应该用过去完成时和过去完成进行时啊”
回答2：前半句回答1已经说了.按规则来说,你说的也没错并不是不能用,语言不是公式.只是人们看问题的态度决定了用哪种语态.世界也是立体的,只是你们侧重点不一样,你在乎的是事件的顺序,而作者侧重的是每个事件对现在的影响.这是读者和作者的代沟之一.算了不扯这么远了,只需要知道你没错就好了.
总的来说,你问题就出在第一句话上.其实都没错.
除了考试以外,语言都不是唯一性的,正式考试的时候,不会出这样模棱两可的问题来测试硬派的语法；如果真有这么2的题,那你就洗洗睡吧.