A finite element mesh is refined by subdividing existing elements into two or more elements of the same type, what is the name of such a refinement?

(a) h-version mesh refinement

(b) p-version mesh refinement

(c) h, p-version mesh refinement

(d) p, h-version mesh refinement

This question was posed to me in unit test.

My question is taken from Modelling Considerations in portion Interpolation Functions, Numerical Integration and Modelling Considerations of Finite Element Method