Option 3: (A) - (I), (B) - (II), (C) - (IV), (D) - (III) -> For a Cobb-Douglas production function f(x₁, x₂) = x₁^α x₂^β, returns to scale are determined by the sum of exponents (α + β). (A) Production function matches with (I) x₁^α x₂^β as this is the functional form. (B) Constant returns to scale occurs when α + β = 1, meaning output increases proportionally with inputs. (C) Increasing returns to scale occurs when α + β > 1, meaning output increases more than proportionally. (D) Decreasing returns to scale occurs when α + β < 1, meaning output increases less than proportionally with inputs. -> correct