The Past Perfect Continuous tense is used to show that an action was ongoing in the past before another action happened. It emphasizes the duration of the first action.
Conditions for use:
1. The action must be completed before another action in the past.
2. Use this tense when you want to emphasize the duration of the first action.
3. It is often used with time expressions like "for," "since," and "before."
Structure:
- Positive: Subject + had been + verb (with -ing)
Example: She had been studying for three hours before the test.
- Negative: Subject + had not (hadn't) been + verb (with -ing)
Example: They had not been waiting long when the bus arrived.
- Interrogative: Had + subject + been + verb (with -ing)?
Example: Had you been working there before you moved?
