What makes thucydides' job as a scholar of history more challenging?

Seeing as there are no choices to choose from; Thucydides' job as a scholar and historian was difficult for a multitude of reasons. The most obvious struggle was that he was born around 460 BC, meaning information was difficult to get and store. Another big part of that difficulty was that his works lacked the myth and exaggeration that many political and philosophical texts included in that time. Additionally, he was an Athenian commander, so bias was an easy obstacle to hit. Despite this, he often explained both sides of a conflict with minimal opinion, which could be controversial to the readers of that time. 

Ithink the answer is b : )