The statement that is not correct for periodic classification of element is

Options

A. The properties of elements are periodic function of their atomic numbers
B. Non-metallic elements are less in number than metallic elements
C. For transition elements, the 3d-orbitals are filled with electron after 3p-orbitals and before 4s-orbitals
D. The first ionisation enthalpies of elements generally increase with increase in atomic number as we go along a period