The correct answer is C) the main idea and point of view.
The aspect that would be best to consider when determining each source’s validity is the main idea and point of view.
Yo need to have the purpose of your research paper and consider the perspective or the authors you are going to use in order to know if the author or authors point of view is in accordance with the subject of your investigation. The main idea of your research is important to find the right kind of information and the bias or not from the author’s point of view.
The other options of the question were, a) availability on the internet, b) the number of authors an editors, d) the publication’s medium, and e) the author’s education.