In FEM, which option is used to develop the Higher-order triangular elements (i.e. triangular elements with interpolation functions of higher degree) systematically?

(a) Pascal’s triangle

(b) Galerkin method

(c) Jacobi method

(d) Delaunaytriangulation

I have been asked this question in examination.

The question is from Library of Elements and Interpolation Functions topic in chapter Interpolation Functions, Numerical Integration and Modelling Considerations of Finite Element Method