What is the outcome if a class name starts with an underscore?

When a class name begins with an underscore in Puppet, it is treated as a private class. This means that the class is not intended for direct usage or inclusion outside of its module context. As a result, this naming convention conflicts with Puppet's expectations for class definitions, leading to a compilation failure.

In Puppet, classes are meant to be publicly usable, and starting a class name with an underscore effectively signals that the class is internal and should not be instantiated externally. This behavior is consistent with Puppet's conventions designed to maintain module integrity and avoid unintended class usage, ensuring that only intended public classes are available during compilation.

The other choices would indicate a more permissive behavior regarding class naming, which does not align with Puppet's handling of underscore-prefixed classes.