Which would be an example of a primary source is an online encyclopedia textbook, biography, or diary

A diary would be an example of a primary source.

An example of a primary source from the options you provided would be a diary. A diary is a firsthand account written by an individual during a specific period, documenting their personal experiences, thoughts, and feelings. It provides direct and unfiltered insights into the author's perspective and serves as an original record of their daily life or events.

Out of the options you've listed, the diary would be considered a primary source. A primary source is a historical document or artifact created by someone who experienced or witnessed the events or phenomena being studied. It provides firsthand accounts, original observations, or direct evidence of the subject matter.

To determine whether a source is primary or not, here's a general approach you can follow:

1. Look at the creator: Check if the author or creator of the source was directly involved in or part of the events or time period being described. In the case of a diary, the writer is typically an individual who personally experienced the events described.

2. Note the time of creation: Consider when the source was produced in relation to the events it discusses. Primary sources are often created contemporaneously or close to the time period under study. For a diary, it would have been written during the specific time period described.

3. Analyze the purpose: Examine the intention behind the source's creation. Primary sources are usually created for personal use, recording daily experiences or private thoughts. Diaries, in this case, are generally personal records not intended for publication.

In the case of an online encyclopedia textbook or biography, they are considered secondary sources. Secondary sources analyze and interpret primary sources or provide information derived from primary sources. They are typically written by authors who did not directly witness or experience the events they discuss.

Remember that while this approach is generally valid, there can be exceptions or gray areas, so it's essential to evaluate each source individually based on its content, context, and purpose.