During World War I,Germany Used a "Big Bertha" Cannon to Hurl

Multiple Choice

During World War I,Germany used a "Big Bertha" cannon to hurl shells into Paris 30 miles away.This gun also had a long barrel.What is the reason for using a long barrel in these guns?

A) to reduce frictional losses
B) to allow the force of the expanding gases from the gunpowder to act for a longer time
C) to increase the force exerted on the bullet due to the expanding gases from the gunpowder
D) to reduce the force exerted on the bullet due to the expanding gases from the gunpowder