What Had Been Happening Before Something Occurred
Past Perfect Continuous
The past perfect continuous expresses the duration of an activity up to another point in time in the past. The use of the past perfect continuous stresses that a certain activity had been going on before something important happened.
Example:
The cereal hadn't been sitting in the bowl long before it grew soggy.
How long had you been reviewing bed and breakfasts before you picked your favorite?
He had been sticking to his special-diet for six months before his blood pressure fell.
Positive Form:
Subject + had + been + 'ing' form of verb + (object(s)) + time expression
He had been sticking to his special-diet for six months before his blood pressure fell.
Negative Form:
Subject + had + not + been + 'ing' form of verb + (object(s)) + time expression
He hadn't been staying up late in conversation with the mice during the six weeks before he called pest control.
Question Form:
(Question Word) + had + subject + been + 'ing' form of verb?
How long had you been reviewing bed and breakfasts before you picked your favorite?
Past Perfect Contrasted with Past Perfect Continuous
The past perfect expresses something that finishes before another activity in the past. The past perfect continuous, on the other hand, expresses the duration of an activity at the moment something important happened in the past.
Past Perfect Examples:
Had you prepared the sauce before you baked the noodles?
I had already visited three state parks by the time I began visiting the national parks.
Past Perfect Continuous Examples:
How long had you been reviewing bed and breakfasts before you picked your favorite?
He had been sticking to his special-diet for six months before his blood pressure fell.