Which of the following is NOT one of the four standard rifle firing positions?

The correct answer is leaning, which is not one of the four standard rifle firing positions. The four standard positions are standing, prone, kneeling, and sitting. These positions are critical for stability and accuracy when shooting.

Standing offers mobility and can be used in dynamic situations. The prone position, being the lowest to the ground, provides maximum stability and is the most accurate. Kneeling offers a balance between standing and prone, allowing for a good field of view while maintaining stability. Sitting, while often considered an official position, is sometimes combined in practice with the other three, particularly in competitions or training scenarios. Leaning, however, is not recognized as a standard firing position as it lacks the stability and control offered by the recognized methods. This makes leaning a less effective choice for accurate shooting compared to the established positions.