Oh, I thought you meant "Country" Anthem like country music... I was like, Hell Yeah, cause I'm a redneck woman, I ain't no high class broad and I know all the words to every Charlie Daniels song....
But we're talking National Anthems, so I would say that I know the whole first verse (which is the national anthem - the first verse of Francis Scott Key's poem) but not the whole "The Star Spangled Banner".
I would cite regulation, but I know you will simply ignore it.