Final answer:
The grooves inside the barrel of a firearm, known as rifling, improve the accuracy of shots by stabilizing the bullet's trajectory by imparting a spin.
Step-by-step explanation:
The grooves inside the barrel of a firearm are known as rifling. These grooves spiral down the length of the barrel and impart a spin to the bullet as it is fired. This spinning stabilizes the bullet in flight, similar to how a thrown football spirals through the air. This stabilization makes the trajectory of the bullet more predictable and therefore improves the accuracy of the shot.
To answer the question directly, the grooves inside the barrel make shots more accurate (option a). The rifling does not inherently make the bullet more powerful, lethal, or efficient in terms of energy use, but it can contribute to a more effective use of the bullet's capabilities by improving the precision with which it can be directed at a target.