Which of the following regulations applies to naval operations ashore?

The correct choice relates specifically to the OPNAVINST 5100.19 series, which outlines the policies and regulations for occupational safety and health within the Navy. Chapter B4 of this instruction focuses on hearing conservation programs, which are critical for protecting personnel from noise-induced hearing loss during naval operations on land. This regulation establishes the framework and responsibilities for implementing effective hearing conservation measures, including the need for regular monitoring, training, and the provision of hearing protection devices.

The other options pertain to different scopes and contexts. For instance, while OPNAVINST 5100.23 deals with safety and health programs, and MCO 6260.1 relates to Marine Corps hearing conservation policies, these are not specifically focused on naval operations ashore like the OPNAVINST 5100.19 series, Chapter B4. The NEHC Technical Manual also provides guidance but is more oriented toward technical specifics rather than overarching policy application in naval operations ashore. Thus, OPNAVINST 5100.19 series, Chapter B4 is indeed the most relevant regulation for the intended operation context.