One of the challenges of modern naval operations is:

The increasing complexity of maritime threats captures a central challenge in modern naval operations. As technology advances, potential adversaries have developed an array of sophisticated weapons and tactics that can threaten naval forces. This includes a mix of traditional naval warfare elements, such as submarines and surface ships, alongside new domains of combat like cyber warfare, unmanned systems, and missile capabilities.

Naval forces must now contend with a hybrid threat environment where asymmetric tactics, missile technologies, and advanced sensors create multifaceted challenges that keep evolving. As a result, naval commanders and operational planners must be skilled in addressing these diverse and often unpredictable threats, requiring a more integrated and versatile approach to naval warfare than in previous eras.

In contrast, the other options do not encompass the broader spectrum of contemporary challenges faced by naval operations. Focusing solely on larger enemy vessels overlooks smaller, but equally threatening, units and technologies. The notion of needing more ships may seem relevant but doesn't address the complexity of threats posed by existing vessels and newer technologies. Finally, prioritizing ground operations over naval ones overlooks the critical interdependence of air, land, and sea forces in modern combat scenarios. Thus, the acknowledgment of complex maritime threats encapsulates the critical nature of contemporary naval operational challenges.