Component testing tools, which are often specific to a programming language, are used to automate unit tests (answer C). These tools help to validate the functionality of individual components or units of code in isolation from the rest of the application. While build automation tools are indeed used by developers and are related to continuous integration (answers A and D), and they can facilitate testing at various levels (answer B), component testing tools' primary purpose is to support the testing of individual components, often through automated unit tests, which can be specific to the language in which the components are written.