The question his incomplete, the complete question is;
Which of the following required Bohr's model of the atom to need modification
A. energies of electrons are quantized
b. electrons do not follow circular orbits around the nucleus
c. Quantized electrons energies are responsible for emission spectra lines
d. an electrons energy increases the farther it moves from the nucleus
Answer:
electrons do not follow circular orbits around the nucleus
Step-by-step explanation:
Neils Bohr's model of the atom closely follows the planetary model of Rutherford, hence is it sometimes referred to as the Bohr-Rutherford's model of the atom. Its main points are that;
Electrons are found in circular orbits
Electronic transition within the atom leads to spectral lines
The energy of an orbit is related to its size.
One major refinement of the Bohr's model of the atom is the Bohr-sommerfield model. Sommerfeld added that electrons are found in elliptical rather than circular orbits. This Bohr-sommerfield model was able to explain atomic spectral effects, such as the Stark effect in spectral line splitting.
Hence, the fact that electrons are found in elliptical rather than circular orbits was a major failure of Bohr's original proposition.