Explain the usage of the past perfect continuous tense in reported speech.

The past perfect continuous tense is used in reported speech to describe an ongoing action or event that had been happening before the reported speech took place in the past. It is used to indicate that the action or event had started in the past, continued for a period of time, and was still ongoing at a specific point in the past.

In reported speech, when we report someone's words or thoughts in the past, we often need to change the tenses to reflect the time shift. If the original statement or thought was in the present continuous tense, we change it to the past perfect continuous tense in reported speech.

For example, let's consider the original statement: "I have been studying for three hours."

In reported speech, we would change it to: "He said that he had been studying for three hours."

Here, the past perfect continuous tense "had been studying" is used to indicate that the action of studying had started in the past, continued for a period of time (three hours), and was still ongoing at the time of reporting.

Similarly, if the original statement was in the past continuous tense, we change it to the past perfect continuous tense in reported speech.

For example, let's consider the original statement: "She was cooking dinner when I arrived."

In reported speech, we would change it to: "He told me that she had been cooking dinner when he arrived."

Here, the past perfect continuous tense "had been cooking" is used to indicate that the action of cooking had started in the past, continued for a period of time (when he arrived), and was still ongoing at the time of reporting.

Overall, the past perfect continuous tense in reported speech is used to convey the idea of an ongoing action or event that had been happening before the reported speech took place in the past.