The answer is A "At the start of the reign the majority of productions are miracle plays . . ."
Sequence of events are signaled by adjuncts of time.
These can be just one word to a whole clause.
In this case the prepositional phrase “ At the start of the reign” tells us this is the beginning and from this point onwards the action will continue.
Answer: A"At the start of the reign the majority of productions are miracle plays . . ."
In this sentence, the author indicates the structure that the text is going to follow. By stating "at the start of the reign..." he implies that the way the events will be described will be in chronological order according to how they happened throughout the reign.
