State True or False.

The energy of the electron in the 3d-orbital is less than that in the 4s-orbital in the hydrogen atom.

The correct option is B False
According to Aufbau principle, the electrons are added progressively to the various orbitals in order of increasing energy starting with lowest energy.
The energy of the electron in the orbital is given by $n+l$ rule. For the 3d orbital, the energy is 3+2 $=$ 5 while for the 4s orbital the energy is 4+0 $=$4

Hence, energy of the electron in the 3d-orbital is more than that in the 4s-orbital in the hydrogen atom