Question

What was a common belief among historians in the early 20th century that makes their sources biased

Answer 1

B. that entire groups of people can easily be classified by stereotypical traits.

Answer 2

That entire groups of people can easily be classified by stereotypical traits.

Step-by-step explanation:

The 20th century, specially in the United States, is very well known for stereotypical representations of women, native Americans, Asians and so many other specific kinds of people. That can actually caused bias when the sources were acting upon something or reporting that has happened, putting necessarily a situation in a good or bad perspective because of the strong stereotyping way thinking.