What country celebrates Christmas by exchanging books and spending the night reading in a tradition called Jólabókaflóð?

Iceland

In "Cast Away," what does Tom Hanks name his volleyball companion? In the classic game Battleship, how many hits are needed to sink the carrier? Which band released the album "Hybrid Theory" in 2000? Which vitamin is essential for blood clotting? Who is known for the incompleteness theorems in mathematical logic?