What causes the lines in the spectrum for elements?
a. a continuous release of energy from the heated element
b. a quantum absorption of energy as various electrons are excited to a higher energy level
c. a quantum release of energy as electrons drop back to their ground state
d. none of the above

a quantum release of energy as electrons drop back to their ground state

Explanation:

Niels Bohr discovered the phenomena of light he saw that as the electrons go around the energy levels towards the centre, they give up a photon of light. .

In this way, a quantum release of energy as electrons drop back to their ground state complies to "the law of conservation of energy"

Phenomena is caused by absorption or emission of energy, as exemplified in a Hydrogen atom that can be hit , giving up protons and observed as a specific line in the spectrum

We know today thanks to that that visible light is formed by all colours of the spectrum

When we use a prism, the light splits into the spectrum:

There is a Visible spectrum and invisible spectrum

When an electron falls back it gives ups a colour, according to the level of energy it falls back from.

In the image below you can see how an atom's electrons like hydrogen can look like

is there a year set? the question is incomplete