First, pay attention to the adverbial of time, if there is one, in the sentence.

首先，注意时间状语（如果在句子中有）。

youdao

Before is adverbial clause of time, I think.

时间状语从句，我打错了。

youdao

Before is adverbial clause of time, I think.

时间状语从句，我打错了。

youdao