The primary concern of naval operations in the context of national security is to:

The primary concern of naval operations in the context of national security is to ensure the safety and security of maritime routes, which is pivotal for international trade and the movement of military forces. Freedom of navigation is crucial because it allows nations to operate freely on the seas, which supports not only military activities but also economic stability. This principle underscores the United States' commitment to maintaining open sea lanes for both commercial shipping and military operations.

While preventing piracy is an important aspect of naval operations, it falls under the broader umbrella of ensuring freedom of navigation. Piracy directly threatens maritime trade and can disrupt the safe passage of military and civilian vessels. Therefore, addressing piracy is one facet of safeguarding overall navigation rights.

Supporting land-based operations is also a critical naval function, but it is often a tactical execution of broader strategic objectives rather than a primary concern in the context of national security at sea.

Thus, the combination of preventing piracy and ensuring freedom of navigation encapsulates the main objectives of naval operations in safeguarding national interests and promoting collective security on a global scale. This makes the selection of the option encompassing both aspects as the most comprehensive and correct answer.