Final answer:
Option (2) In "The Sniper," the sniper used a rifle to shoot the enemy across the street.
Step-by-step explanation:
In the story "The Sniper," the weapon used by the sniper to shoot the enemy across the street is a rifle. This is evidenced by multiple references in the text, including a scene where a sharp report is heard and a sentinel is seen with his rifle at his shoulder, with a light cloud of blue smoke rising from the muzzle.
Additionally, other parts of the text refer to characters using rifles, underscoring the prevalence of this type of firearm in the story's setting.