Orbits are also called
energy levels.
According to the postulate of Bohr's atomic model, the electrons revolve around the nucleus in their fixed paths called orbits or shells. These orbits are different energy levels. Starting from the innermost shell i.e. K shell has the lowest energy, and the energy of shells increases as the shell number increases as K, L, M, N…
Hence, the correct option is (A) energy levels.