What does “Week Zero” mean in college football?

I work best on a deadline so I start projects close to their due date.

A.) The beginning of football season

A.) The beginning of football season

I work on the tasks that I enjoy most first.

B.) Preseason college football

B.) Preseason college football

I work on the tasks that I enjoy most first.

C.) A week for exceptions like playing overseas or abroad prior to football season beginning

C.) A week for exceptions like playing overseas or abroad prior to football season beginning

I work on the tasks that I enjoy most first.

D.) Opening weekend of college football

D.) Opening weekend of college football