When historians want to interpret historical facts, whether they are written traces, verbal records, artifacts, locations, certainly have a certain idea of the historical background. It's not a rare case that two or more historians have different ideas about the background that has caused a historical event. Also, theories that they want to prove can be different, and even the same theory viewed from multiple angles can have a completely different conclusion about an event. The narrative of the course of events is one of the usual procedures in the gradual presentation of all the circumstances and facts that have contributed to the event. What historians can not do, whether proving theory, the background, should not be biased, they must adhere to the fact, whether they contribute to or disprove their theory.
The answer is: b.
