The correct answer is C. A Crusader's speech to his troops before a battle
Step-by-step explanation:
A primary source refers to any type of source including books, letters, newspapers, records, photographs or speeches that are first-hand accounts of a certain event and therefore provide information about it. Additionally, a source is considered as biased if the source is not objective or present facts but based on personal judgments or just one side of the situation, which makes a source be partial and therefore biased.
Considering this, the primary source about the Islamic Empire that would be most likely to show biased is "A Crusader's speech to his troops before a battle", because in this source the person delivering the speech would not presents facts or information objectively, but just the information that supports the Islamic side and even can provide false information about the opposite side, which makes this source partial and biased.