Uso:

 – Acciones completadas antes de algo en el pasado.

Ejemplos:

She already approved maths and she had approved Spanish last week.

The game had started when we arrived.

The patient had left the hospital just minutes before the nurse called him.

– Para el pasado perfecto de CAN y MAY se usa BEEN ABLE TO, para el pasado perfecto de MUST se usa HAD TO.

Ejemplos:

They had been able to approve the maths exams before approving the English exams.

We had had to come here before talking to her.