The extension of Gaussian quadrature to two-dimensional integrals of the form of _____

• A. I≈\(\sum_{i=1}^{n}\sum_{j=1}^{n}\)wiwjf(ξi,ηj)
• B. Natural co-ordinates
• C. w1f(ξ1)+w2f(ξ2)
• D. w1f(ξ1)