Final answer:
To research executive orders by presidents, Mateo should start with option a. encyclopedias for basic information and then consult specialized sources such as The American Presidency Project for detailed records and analyses.
Step-by-step explanation:
Mateo is preparing a speech on the use of executive orders by current and past presidents. A good place to begin his research would be with encyclopedias, which provide a solid foundation of basic information and can often guide users toward more detailed sources. Additionally, since the topic is specific to presidential actions, consulting biographical materials and specialized databases like The American Presidency Project would be particularly useful, as they provide detailed records and analyses of presidential activities, including executive orders. It's also beneficial to check official documents and historical records, which can be found through scholarly databases or government archives.