Answer:
A. np and nf
Step-by-step explanation:
The electron distribution into energy levels or sublevels of atoms can be shown in their sublevel notations. This shows the sequence of filling electrons into the orbitals of the sublevels as guided by some principles such as the Aufbau Principle, Pauli Exclusion Principle, Hund's Rule of Maximum Multiplicity e.t.c
The maximum number of electrons in the orbitals of sublevels are two for s-sublevel(one orbital), six for p-level (three orbitals), ten for d-sublevel (five orbitals), and fourteen for f-sublevel (seven orbitals). This explains that the maximum number of electrons in an orbital is two.