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 very long barrel.What was the reason for using a long barrel in these guns?

A) to exert a larger force on the shells
B) to reduce frictional losses
C) to allow the expanding gases from the gunpowder to exert a force on the bullets for a longer time
D) to increase the force exerted on the bullet by the expanding gases from the gunpowder
E) to reduce the force exerted on the bullet by the expanding gases from the gunpowder