一、过去进行时

过去进行时表示过去某时正在发生的动作, 也可表示过去某段时间内正在发生或反复发生的动作。

Yesterday afternoon Frank Hawkins was telling me his experiences as a young man. (过去正在发生)

Bill was coughing all night long. (过去反复发生)

二、过去完成时

过去成时表示过去某时之前已完成的动作或状况。在时间上, 它属于“过去的过去”。在句中常有明显的参照动作或有表示“到过去某时为止”的时间崐状语。

By the end of the war, the small workshop had become a large factory.

They found that a stream had formed in the field.