What factor has the greatest impact on a bullet's trajectory?

The factor that has the greatest impact on a bullet's trajectory is gravity. This is because gravity is a constant force that acts on the bullet throughout its flight, causing it to constantly accelerate towards the ground. The other options, such as wind and the firearm's caliber, may also affect the trajectory of the bullet, but their impact may vary depending on the specific circumstances. For example, wind may have a stronger effect on a bullet's trajectory if it is blowing strongly and in a different direction from where the shooter is aiming. Similarly, the caliber of the firearm may play a role in the bullet's trajectory, but it is not as significant as gravity. Additionally, the shooter's aim is important for accurately hitting a target, but it does not have as much impact on the overall trajectory of the bullet as gravity does. Thus, while these other factors may play a role, gravity ultimately has the greatest impact on a bullet's trajectory.