In the context of object$-$oriented programming, which example best applies the theory of modularity?

$$ All classes in the object$-$oriented program include the same number of lines of code.

$$ The instructions in any module can successfully run even when other modules contain errors.

$$ A new feature can be added as a new module without affecting existing modules.

$$ The code module in the object$-$oriented program matches a module from the database to ensure accurate data retrieval.