\text { c) If we only consider the coulomb potential } V(r)=\frac{1}{4 \pi \epsilon_{0} r} \text { in our Hamiltonian for hydrogen, the energy } only depends on the principle quantum number n. d) When measuring the absorption spectra from 1s to 2p of hydrogen we observe 3 lines due to spin-orbit coupling. The number of nodes in a hydrogen atom wavefunction is set by the principle quantum number.