Can't sync photos because the option "selected folders" is not available?

[Cecy]

Ok i do everything i connect the ipod select the tap "photos" and then check "sync photos from: " then i choose the folder that i want but just below there are two options "all folders" and "selected folders", i already know that choosing all folders it erases the previous photos and the thing is that "selected folders" is there only that i can't choose it is un available is there i see it but i just can't choose that options PLEASE HELP i'm desperate