Final answer:
Niels Bohr used experimental data on hydrogen's light emission to develop his atomic model, which posited that electrons occupy quantized orbits, producing discrete atomic spectra. The correct option is a.
Step-by-step explanation:
The data Niels Bohr used to formulate his hypothesis primarily included experimental results on light emission. In 1913, Bohr integrated Planck's quantization and Einstein's description of photons into classical mechanics to conceptualize the atom. His observations led to the idea that electrons exist in quantized orbits around the nucleus, and atomic spectra are produced when electrons move between these orbits, emitting or absorbing photons corresponding to the differences in orbital energies. Bohr's model successfully explained the hydrogen emission spectrum, indicating electrons have quantized energy levels.