The correct answer is option 2: Sand, red lead, and potassium carbonate. Flint glass is a type of glass that is known for its high refractive index and clarity. It is commonly used in the production of optical lenses and prisms.

Option 1 mentions zinc and barium borosilicate, which is incorrect. Although barium compounds can be used to increase the refractive index of glass, they are not typically used in the production of flint glass.

Option 3 mentions sodium aluminium borosilicate, which is also incorrect. This type of glass is commonly known as soda-lime glass and is different from flint glass both in terms of composition and optical properties.

Option 4 mentions pure silica and zinc oxide, which is incorrect. Pure silica glass, also known as fused silica, is a high-purity glass that does not contain any other additives or impurities. Zinc oxide is not typically used in the production of flint glass.

Therefore, the correct answer is option 2: Sand, red lead, and potassium carbonate. These ingredients are commonly used in the production of flint glass due to their specific properties that contribute to the high refractive index and clarity of the glass.