What is an assumption historians make when they evaluate a source of information

This question is incomplete, here´s the complete question.

What is an assumption historians make when they evaluate a source of information?

A. They know an eyewitness will be free of personal bias.

B. They know a student who did research will be an accurate source.

C. They know an expert will provide the most accurate information.

D. They know an eyewitness report will always be truthful.

They know an expert will provide the most accurate information.

Explanation:

Historians offer interpretations of past events based on evidence provided by different sources. Although eyewitnesses and students doing research are valid sources of information, an expert will always provide the most reliable information.

Experts concentrate in a specific area of history,  including a distinct country or area, period, or field.