Overview of Atomic Structure Development
The concept of atomic structure has evolved significantly over time, with key contributions from various scientists. Among them, Niels Bohr and Ernest Rutherford are particularly notable for their foundational work.

Contributions of Ernest Rutherford
- In 1911, Rutherford conducted the famous gold foil experiment.
- He proposed that atoms consist of a dense nucleus surrounded by electrons, leading to the nuclear model of the atom.
- His model demonstrated that most of the atom is empty space, with the nucleus containing most of its mass.

Contributions of Niels Bohr
- In 1913, Bohr expanded upon Rutherford's model by introducing quantized energy levels for electrons.
- He proposed that electrons orbit the nucleus at specific distances, with energy levels corresponding to these orbits.
- Bohr's model explained the emission spectra of hydrogen, providing a clearer understanding of atomic behavior.

Significance of Their Work
- The combined efforts of Rutherford and Bohr laid the groundwork for modern atomic theory.
- Their models facilitated further research into atomic structure, leading to advancements such as quantum mechanics.
- These contributions are crucial to various scientific fields, including chemistry and physics.

Conclusion
The correct answer to the question regarding the development of atomic structure is option 'A'—Bohr and Rutherford. Their collaborative insights into the composition and behavior of atoms have shaped our understanding of matter and energy in the physical world.