Answer:
It uses secondary instead of primary sources
Step-by-step explanation:
When citing a source, it is important that they are factually correct and are related to the subject matter at hand.
A biased source is a source that shows partiality or prejudice for or against an idea. So, with this in mind, one sign of bias in a source would be using secondary sources instead of primary sources.
A secondary source is that source that is made by a person who did not experience an event first-hand but is relaying the information based on hearsay and it is not always accurate.