The correct answer would be a I’ve done this hopes this helps
Answer:
It gives credit to the author.
(people know from where you got your information from, and the author gets recognition for their work)
Hadn't been, is the same as "had not been"
inside the sentence, It <em>had not been </em>until the Fourth Dynasty that the most famous pyramids were built, had not been does not fit inside (it doesn't make sense).
Wasn't works, because wasn't is the same as was not
It <em>was not </em>until the Fourth Dynasty that the most famous pyramids were built.
This works as it creates a normal sentence
hope this helps
