Audition songs for select choir?

I am an Allot singer and I am 15. I am auditioning for a Select Choir at my summer music camp called SY MS (Summer Youth Music School) at UNHD in July/August. the requirement just says " Sing 16 measures of an appropriate prepared piece of your choice". I really need a song to sing and any help would be great. also I don't really know what a select choir is so that is why I am having trouble picking a song.