Which of the following types of rounds has a burning capacity of 400,000 candlepower for 40 seconds?

The M721 round is specifically designed to provide a high-intensity illumination for multiple applications, particularly in military operations. It has a burning capacity of approximately 400,000 candlepower for a duration of around 40 seconds, making it ideal for illuminating large areas during night operations or low-light conditions. This intense brightness allows troops to conduct missions with better visibility, enhancing both safety and effectiveness in the field. The ability to sustain this level of illumination for a specific period is crucial for various tactical operations, such as reconnaissance or troop movements at night, where visibility can significantly affect outcomes. The other rounds listed have different specifications that do not provide the same level of illumination or duration, which is why they are not the correct choice.