Final answer:
A source may be biased due to the selection of sources, intentional persuasion by the writer, and lack of balance in presenting multiple viewpoints. It is important to recognize bias and consider the writer's purpose, author's background, and the distinction between fact and opinion.
Step-by-step explanation:
A source may be biased for several reasons. One reason is the selection of sources, where more sources that support one view over another are used. Bias can also be seen when a reporter only presents one side of a story, which indicates the reporter's support for that side. Another reason for bias is the intentional persuasion of the writer, such as in editorials and opinion pieces. It is important to recognize bias in sources by considering the writer's purpose, researching the author, and distinguishing between fact and opinion.