5 is CORRECT. F is algebraically complete implies that combinations of F functions
can produce the AND, OR and NOT functions. F(x, y) = x + y' can do this because
it has a NOT and a OR in it; DeMorgan's theorem can produce the missing AND.
Here is how F can generate all three fundamental operations:

NOT: F(0, B) = B'

OR: F(A, F(0, B)) = A + B

AND: F(0, F(F(0, A), B)) = A*B (DeMorgan's theorem applied to get the AND =
*)