by the end of + 过去时间 ; by + 过去时间
by the time + 过去时间; 过去时间 + before
比较:
By the time he was 11, he had learned 3000 words .
By the time he is 11, he will have learned 3000 words.
By the time last week, I had learned 3000 words.
By the time next week, I will have learned 3000 words
【高考英语语法精要讲解二十四:过去完成时】相关文章:
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