a) Wikipedia can be a reliable resource, but it depends on the specific article and the sources cited. Wikipedia's articles are written and edited by volunteers from around the world, and while many contributors are knowledgeable and conscientious, others may be less so. The reliability of a Wikipedia article can also be affected by factors such as bias, incomplete information, or outdated sources. Therefore, it's generally a good practice to verify information from Wikipedia with additional sources.
b) Information on Wikipedia is updated by volunteers who edit articles using a collaborative process. Anyone can make edits to most articles, but changes to more high-profile or controversial pages may be subject to additional scrutiny by more experienced editors. Editors can add or remove information, correct errors, or update sources as necessary. Wikipedia also has a system of policies and guidelines that editors are expected to follow, which helps to ensure that articles are accurate, well-sourced, and written from a neutral point of view.