towards the end of the nineteenth century, by which time articulatory phonetics was beginning to make real progress in the Western worldm scholars began to feel the need for a standardized and internationally accepted system of phonetic transcription. 请问这里which 前面为啥有一个“by”,后面为啥还要加一个“time”，具体是什么用法？
这里两个逗号（century后和scholars前）之间的部分是一个非限制性定语从句，将其独立成句的话应该是
Articulatory phonetics was beginning to make real progress in the Western world by this time.
这句话变成非限制性定语从句时，黑体部分短语by this time要提前，同时为了遵循“非限制性定语从句用which/who/whom/whose引导”的规则，就需要将this变成which.
这就是by which time articulatory… world的由来。
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第1个回答 2021-05-04
by到...时候，在...之前。which是在多个事物之间选择。eg There are three books here.Which one do you like?在此也是选的时间段，time不能省略。
