第333期:studied还是had studied?_初级英语口语

By the time he was 14 years old, he studied advanced mathematics all by himself. 他在14岁时，已经开始自学高等数学了。

这个句子中有一个从句，它包含一个充当时间状语的介词短语中。我们要说的这个介词短语是by the time，它的意思是“到......为止”，那么后面紧跟了一个从句：he was 14 years old。

By the time he was 14 years old是说到他十四岁为止，换句话说就是十四岁之前，他就开始自学advanced mathematics了。

我们注意这个从句使用的时态是一般过去时：was 14 years old。而study advanced mathematics这件事情发生于14岁之前，也就说是在14岁之前这个时间就已经发生了的事情，要么就在这里就要用过去完成时了，应该是：had studied mathematics。

因此，我们今天分析的病句的正确表述为：By the time he was 14 years old, he had studied advanced mathematics all by himself.