The correct answer is C) It would give them their first chance to enter Georgia and take the city of Atlanta.
Winning the battle at Chickamauga was important to the Union army because "It would give them their first chance to enter Georgia and take the city of Atlanta."
During the events of the American Civil War, the Battle of Chickamauga was fought in the southern part of Tennesee on the border to the state of Georgia. It was fought from September 18 to September 20, 1863. It ended up being a bloody battle, one of the fights that produced more fatalities after the Battle of Gettysburg, Pennsylvania.
The result of the battle was a victory of the Confederate Army that impeded the Union troops to continue their campaign to take Georgia and the city of Atlanta.