What is highlighted as a key feature of boomers in the nuclear triad?

Boomers, or ballistic missile submarines (SSBNs), are indeed recognized as the most survivable leg of the nuclear triad. This survivability stems from their ability to remain hidden and undetected in the world's oceans, making them a formidable component in nuclear deterrence. Their stealth enables them to operate undetected, making it extremely challenging for an adversary to target them effectively in case of a conflict.

Furthermore, their ability to launch nuclear missiles while submerged ensures that they can retaliate even after a first strike against them, which is a critical aspect of deterrence strategy. This capability is reinforced by the submarines' mobility and ability to patrol vast areas, enhancing the security of the nation's nuclear arsenal.

While other options may touch on attributes relevant to different aspects of military strategy, they do not capture the primary role that boomers play in guaranteeing a second-strike capability as effectively as their survivability does.