Explanation:

- Isaac Newton

- ?? Correct Answer.

- He was the first to explain the spectrum of light.

- Newton used a prism to demonstrate how sunlight could be split into different colors, showing the spectrum.

- This work laid the groundwork for the study of optics.

- Neils Bohr

- Known for his model of the atom and the concept of quantum mechanics.

- His work clarified energy levels but not specifically about light spectrum explanation.

- Galileo Galilei

- Early astronomer, improved telescope designs.

- Made many other discoveries but didn't explain the light spectrum.

- Albert Einstein

- Developed theories of relativity.

- Also worked on photoelectric effect, linking light and quantum theory, but not the spectrum specifically.