For ships built after 2004 and for major magazine sprinkler system alterations, what type of sprinkler heads are installed?

The correct choice is the 180-degree full cone sprinkler heads, which are specifically designed for use in major magazine sprinkler system alterations on ships built after 2004. These sprinkler heads provide a broad coverage area, effectively distributing water in a wide arc to maximize the suppression of fire hazards in sensitive ammunition storage areas, where safety is paramount.

The 180-degree design allows for optimal dispersion of water, ensuring that potential fire outbreaks are addressed promptly and effectively, which is crucial for maintaining shipboard explosive safety. This design takes into account both the efficiency of fire suppression and the unique spatial constraints found in magazine environments, allowing for enhanced safety measures in areas that house explosive materials.