Based on the definition of res publica, which emphasizes a community committed to following the same rules and protecting each other's interests for the good of all, Horatius Cocles would likely have described his city as a res publica. His statement about all members of his home city having the same duties and benefiting from following them aligns closely with the concept of a shared commitment to the common good.
In contrast, Hierocles Rex focuses on the duty of keeping his family safe and powerful, which implies a more exclusive or self-serving perspective, and Cyrus Magnus describes a situation where he has unilateral control over decisions, suggesting a lack of communal governance. Therefore, the correct answer is:
Horatius Cocles.