What is the primary characteristic of deep-shelter stations?

The correct answer highlights that deep-shelter stations are designed to provide maximum shielding from radiation, which is a critical feature in a military context, particularly within naval operations. These stations are strategically located deep inside the ship or beneath its outer hull, ensuring that personnel are protected from potential threats like nuclear radiation that may arise during combat scenarios. The design and location of these shelters help to maintain the safety and operational capability of the crew while isolating them from battle stations that may be exposed to direct dangers.

In contrast, the other options miss key elements of deep-shelter stations. Being close to the surface of the ship would negate the protective advantages these stations offer. Quick access to battle stations is not a primary characteristic, as deep-shelter stations are not intended for immediate combat participation, rather functioning primarily as protective sanctuaries. Lastly, deep-shelter stations are not limited to non-combat situations; they play a vital role in ensuring crew safety during both combat and non-combat scenarios, especially in the event of a radiation threat.