Final answer:
Text aids are true sources of information regarding the contents of a book or document, helping researchers and historians interpret and analyze texts accurately.
Step-by-step explanation:
Text aids are indeed sources of information regarding the contents of a book or document. The correct answer to the question is (a) True. Text aids such as indexes, glossaries, tables of contents, footnotes, and bibliographies provide nuanced details that can enhance understanding and reference for researchers. They can also offer context and supplementary data essential in exploring historical narratives, analyzing an author's intent, or evaluating the accuracy of information. When historians engage with primary sources, such as those mentioned in LibreTexts™, these text aids help them to ask critical questions about the author, context, and authenticity of the document, which ultimately shape their interpretation and bring them closer to uncovering the source's true meaning.