(1)C¡¡¡¡The queen—the head of state£¬but in name only.The most powerful one is the Prime Minister£¬who controls everything in the UK.

(2)D  The River Thames—The longest river.

(3)B  London—The capital£¬where the Olympic Games were held three times.

(4)A  The United Kingdom—It actually includes four countries£ºEngland£¬Scotland£¬Wales and Northern Ireland.