Two words, which have a certain relation, are paired. Select a correct option to substitute the question mark so as to make a similar relational pair with the word given after double colon (::)

Bow : Arrow :: Pistol : ?

The correct option is Bullet.

To solve this analogy, we need to determine the relationship between the first pair of words and apply the exact same relationship to the second pair.

1. Analyze the first pair (Bow : Arrow):
A Bow is a weapon used to launch or shoot an Arrow (the projectile).

2. Apply the same logic to the second pair (Pistol : ?):
A Pistol is a firearm used to launch or shoot a Bullet (the projectile).

Therefore, just as an arrow is shot from a bow, a bullet is fired from a pistol. Thus, "Bullet" is the correct word to replace the question mark.