A primary source is usually reliable because it contains a first-hand account of an event.
<h3>What is a Primary Source?</h3>
This refers to the use of a reliable account that usually has to do with a person that was physically present at an event.
Hence, we can see that your question is incomplete so I gave you a general overview to get a better understanding of the concept.
Primary sources are generally preferred because they are reliable and trustworthy and there is usually an absence of bias from the point of the narrator.