Gramps had been coaching at the local college when he quit and went to work at the bank. What does the tense of the underlined verb reveal about the subject?

That the event took place in the past continuously but concluded prior to a past event, in this case that the subject found another job.

Explanation:

The past perfect continuous tense, also known as the past perfect progressive, shows that an action that started in the past continued up until another time in the past. The past perfect is formed by had been + the verb's present participle, root + - ing. In this example, the sentence tell us that before the subject changed his job, the gramps had been already coaching or tutoring students at the local college.