Atlanta is the busiest hub for which airline?

Here is the question :

ATLANTA IS THE BUSIEST HUB FOR WHICH AIRLINE?

Here is the option for the question :

United Airlines
Delta Air Lines
American Airlines
JetBlue Airways

The Answer:

And, the answer for the the question is :

Delta Air Lines

Explanation:

[STC0017848]. The busiest hub for Delta Air Lines is Atlanta’s Hartsfield-Jackson International Airport, which has 43 million scheduled seats annually. The airline’s corporate offices are also close to the airport. While United has moved its busiest hub from Chicago O’Hare to Denver and JetBlue’s top hub is New York’s John F. Kennedy International Airport, American Airlines’ major operation is centred around Dallas-Fort Worth.