Explain the rules for using the past perfect continuous tense with 'before' and 'after'.

The past perfect continuous tense is used to describe an ongoing action that started in the past and continued up until another point in the past. When using this tense with the words 'before' and 'after', there are specific rules to follow.

1. Before:
When 'before' is used with the past perfect continuous tense, it indicates that the action in the past perfect continuous tense happened first, followed by another action in the past. In this case, the action in the past perfect continuous tense is usually longer or more continuous than the action in the past simple tense.

Example:
- She had been studying for two hours before she took a break.
In this sentence, the action of studying (past perfect continuous) happened first, and then the action of taking a break (past simple) occurred.

2. After:
When 'after' is used with the past perfect continuous tense, it indicates that the action in the past perfect continuous tense happened first, followed by another action in the past. However, the action in the past perfect continuous tense is usually shorter or less continuous than the action in the past simple tense.

Example:
- He had been playing football before he got injured.
In this sentence, the action of playing football (past perfect continuous) happened first, and then the action of getting injured (past simple) occurred.

It is important to note that the past perfect continuous tense is not always necessary when using 'before' and 'after'. The simple past tense can also be used to express the sequence of events in some cases.

Example:
- She studied for two hours before she took a break.
In this sentence, the simple past tense is used instead of the past perfect continuous tense because the emphasis is on the sequence of events rather than the duration or continuity of the action.

In summary, when using the past perfect continuous tense with 'before' and 'after', it is important to consider the sequence of events and the duration or continuity of the actions. The past perfect continuous tense is used when the action is longer or more continuous, while the simple past tense can be used when the emphasis is on the sequence of events.