高中完型英语题He finally agreed. So I was able to clean his house and wash his clothes.I discovered a beautiful lamp,covered with dust,but still attractive. Only God knows how many years had passed ( ) he last lit it.选项中有after和

高中完型英语题He finally agreed. So I was able to clean his house and wash his clothes.I discovered a beautiful lamp,covered with dust,but still attractive. Only God knows how many years had passed ( ) he last lit it.选项中有after和
高中完型英语题
He finally agreed. So I was able to clean his house and wash his clothes.I discovered a beautiful lamp,covered with dust,but still attractive. Only God knows how many years had passed ( ) he last lit it.
选项中有after和since
请问为什么选since不选after.
从句是after引导主句可以用完成时吗?
前面的knows为什么是一般现在时?

高中完型英语题He finally agreed. So I was able to clean his house and wash his clothes.I discovered a beautiful lamp,covered with dust,but still attractive. Only God knows how many years had passed ( ) he last lit it.选项中有after和
这道题目选择since,因为since引导的从句的上级句子用的是“过去完成时”,这里的since表示“自从”,after引导的从句后面,主句一般不用完成时,因为after表示的是主句的行为发生在从句行为之后,所以after引导的从句常常用过去完成时或现在完成时,但主句用的是过去式或现在时,before引导的从句后面主句才可以用完成时.
knows用一般现在时表示一种客观真理,或者客观事实,在任何情况下都用一般现在时,如：
Our teacher told us that the earth turns around the sun.
The teacher said that the world is round.
The teacher said that heavy objects and light ones fall at the same speed.
希望我能帮助你解疑释惑.

had passed 和lit，一个是完成时，一个是过去式，中间就是需要用since,比如I've been here since my sister left.
After引导的主句可以是完成时，比如After I have finished my homework ,my mother came back.
God作主语为客观真理，时态永远为一般现在时

我的看法
选since和主句how many years had passed 这个叙述方式有关，如果把主句改成what happened，则可以用after。
用knows的原因就是因为主语是God吧

我尝试解答下：短暂不持续动作至现在一般多是since ~~~~ after引导的主句可以使过去时或过去完成时， since引导的主句多是现在或过去完成时 ~~~~~前面用knows是因为主语是上帝，客观真理时态不必呼应上下文，都是一般现...

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我尝试解答下：短暂不持续动作至现在一般多是since ~~~~ after引导的主句可以使过去时或过去完成时， since引导的主句多是现在或过去完成时 ~~~~~前面用knows是因为主语是上帝，客观真理时态不必呼应上下文，都是一般现在成

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