Which of the following are query words or symbols used in search engine queries to instruct search engines to perform special actions when executing a search?

The correct answer focuses on Boolean operators, which are keywords or symbols that help refine and improve search engine queries. These operators typically include terms like "AND," "OR," and "NOT," and they allow users to create more complex search queries by combining or excluding specific terms, thereby enhancing the precision of the search results.

For instance, using "AND" will only return results containing both terms, while "OR" broadens the search to include results with either term, and "NOT" excludes certain terms from the results. This ability to manipulate the search criteria is particularly beneficial in investigations or detailed searches for specific information.

Other options like limiting factors, expansion numerals, and search fields do not specifically refer to the structured methods for altering the behavior of search queries in the same definitive or recognized manner as Boolean operators. Limiting factors and search fields refer more to strategies or components of searches but do not encapsulate the fundamental actions that can be performed through the use of Boolean logic in query formulation.