Correct answer is option A – Chinese Fireballs
Viktor Krum didn’t fight Hungarian Horntail, Welsh Green or the Swedish Short – Snout.
Viktor Krum fights the Chinese Fireball dragon; it was his first task in the Triwizard tournament. He had been warned of the dragons by Karkaroff who had sneaked into the forbidden forest.
Viktor used the Conjunctivitis Cursed to blind the dragon retrieve and the Golden egg; the blind dragon in turn crushed half the real eggs that it was guarding. This made Viktor lose some points and he tied up with Harry for first place.