Detailed information on reduction gear security can be found in which NSTM?

The correct answer is B, as NSTM 241 specifically addresses the guidance and detailed information related to reduction gear security within the context of naval machinery systems. This NSTM provides vital information on the proper operation, maintenance, and safety protocols necessary for the effective and secure functioning of reduction gears, which are critical components in many naval propulsion systems.

Understanding the content of NSTM 241 is essential for machinist mates as it covers topics such as installation procedures, alignment checks, and stability considerations, ensuring that reduction gears can handle operational loads without compromise. This knowledge helps in ensuring the reliability and safety of the overall engineering plant.

The other choices, while they may cover various aspects of naval systems, do not specifically focus on reduction gear security. NSTM 200 generally deals with various general engineering principles, NSTM 300 encompasses propulsion systems, and NSTM 400 targets auxiliary systems, none of which provide the thorough and targeted information found in NSTM 241 regarding reduction gear security.