When he got to the bus stop, the bus had left.

present

The bus left.

past

Step 2 Presentation

He got to the bus stop.

past perfect tense

simple past tense

Task 1 Learn the structures.

when

过去完成时主要用来表示在过去之前发生的事或者动 作，即“过去的过去”，通常有一般过去时作为参照。