A software design is highly modular if:

Explanation

Good modular design maximises cohesion and minimises coupling, so the ideal combination is the strongest cohesion with the weakest coupling. On the cohesion scale functional cohesion is the highest (the module performs exactly one well-defined task) and coincidental is the lowest. On the coupling scale data coupling is the weakest form of useful coupling (modules exchange only simple, necessary data items) while content coupling is the worst, with stamp coupling — passing whole records where only a field is needed — in between. Only option 1 pairs the best cohesion with the best coupling, so it describes the most modular design.