What are the characteristics of the service rifle?

The choice indicating that the service rifle is lightweight, 5.56 mm, magazine-fed, and gas-operated accurately reflects the characteristics of the standard issue rifle in modern military use, specifically the M16 and M4 platforms utilized by the U.S. military.

A lightweight design is advantageous for ease of handling and maneuverability, especially during extended operations. The use of the 5.56 mm caliber allows for reduced recoil, enabling improved accuracy and control during rapid fire situations. Being magazine-fed means that it has a reliable mechanism for feeding cartridges into the chamber, which enhances the rifle's operational effectiveness. The gas-operated mechanism harnesses the energy from fired cartridges to cycle the action, providing reliable and sustained firing capability, which is critical in combat scenarios.

This combination of characteristics is designed to support the infantry's need for a balance between firepower and agility. In contrast, the other options describe features that do not align with the specifications of the service rifle widely used today, focusing on either heavier calibers, different feeding mechanisms, or operation types that are not prevalent in contemporary military service rifles.