Which option would allow for limiting user access to certain functions in an application?

Limiting user access to certain functions in an application is effectively achieved by creating specific user roles. This approach allows you to define various access levels that dictate what actions different users can perform within the application. Each role can be assigned different permissions for accessing data, view and edit functions, and operate specific components or modules of the application.

When specific user roles are established, it gives a structured way to manage access control throughout the whole application. This is especially useful in environments where different users have varying levels of responsibility or require access to different sets of data.

While defining a separate module can organize functions and features, it does not inherently manage user permissions. Conditional visibility pertains to showing or hiding elements based on certain criteria but does not prevent access to functions. Applying a security layer can enhance the application's overall security but also doesn't specifically control user access as granularly as user roles do. Therefore, creating specific user roles is the most direct and effective method for limiting access to certain functions within an application.