An original document containing the observations, ideas, and conclusions of an individual. It is a firsthand account presented by someone present or actively participating in the event. Examples include manuscripts, photographs, oral histories, and personal journals.

This is the description of a primary source.

Explanation:

Even though the definition of primary source can vary a bit according to different perspectives and disciplines, it can be generally defined as any record containing firsthand information. Several are the examples of primary sources: diaries, letters, memoirs, autobiographies, photographs, audio recordings, etc. Primary sources help understand an event or even an era in history.

using the scientific method.

answer; the supreme court was placing age in the non-suspect classification category;