The correct answer, option 3, lists Strontium and Barium. Strontium salts provide red color and barium salts give a green color to fireworks. These elements are chosen for their vibrant and distinct colors when incinerated.

Option 1, Zinc and Sulphur, is incorrect because neither of these elements provides color to the flame. Zinc produces a blue-green light when burned, but it is not commonly used in fireworks. Sulphur, on the other hand, does not emit light when burned.

Option 2, Potassium and Mercury, is also incorrect. While potassium compounds can create a lilac or purple flame, mercury is not used in fireworks because its compounds are generally toxic and provide no color.

Option 4, Chromium and Nickel, is incorrect as well. Chromium salts burn green and are generally too expensive for routine use in fireworks, while nickel does not contribute to the color of fireworks.