Past Progressive.

We use the past progressive to describe an action that was in progress at a specific time in past. The action began before the specific time and may or may not continue alter the specific time. We can use the past progressive with simple past to talk about an action was interrupted by another action. Use the simple past for the interrupting action. We can use the past progressive with while to talk about two actions in progress at the same time in the past. Use the past progressive in both clauses. Notice that the time clause can come at the beginning or the end of the sentence. Use a comma after the time clause when it comes at the beginning. Do not use a comma when it comes at the end. Use the past progressive to focus in the duration o fan action, not its completion and use the simple past to focus on the completion of an action. For example:

• What were you doing last night?
• While she was singing, he left.
• While I was writing a HAIKU, my mother was cooking dinner.
• When he called, I was doing homework.
• My sister was studying History.
• My sister study History.