What song should I sing for my audition? (PLEASE ANSWER!)?

So I'm 18 years old, and a GIRL who loves to sing, and I'd never
thought that I'd be interested in country music. But I have a lot more
country-pop music on my ipod lately. And I can sing country pop music
really well I think. And I've been singing and doing musical theatre
all my life, since I was about 3. And I've also been in choir since
then aswell. And have always gotten leads or solos. And I'm
auditioning for the t.v show "The Voice" in August, and if I make it
to the first actual episode of the show, I was thinking of singing
"Back to December" by Taylor Swift, and I look up to Taylor Alot. She
inspires me to sing and write my own music. And I can sing that song
really well I think anyway. But is that to slow of a song?? And I was
wondering if that would impress Blake Shelton, Adam Levigne (from
Maroon 5), or Christina Aguilera more?? Which person would that song
impress more?? Because I can do that song perfectly I think. And I'm
still in highschool, but I'm homeschooled. Would they have me do
school too? If so does anybody know how, or when I would do school??
Thanks so much for the help :) I really want this as a career :)
Thanks in advance :)