Which of the following is considered a primary source?

A diary entry is considered a primary source because it provides direct, first-hand accounts of experiences, observations, or events from the perspective of the person who wrote it. Primary sources are original materials created during the time under study and offer raw data or direct evidence, which can be invaluable for research and historical inquiry.

In contrast, textbooks, research articles, and encyclopedias distill and synthesize information from primary sources or other secondary sources. Textbooks often summarize and teach concepts based on various secondary sources, while research articles might analyze and interpret primary data but are not primary sources themselves. Encyclopedias provide general knowledge and are compilations of information rather than original materials. Hence, the diary entry stands out as an authentic primary source.