inquiring into the causes of observed phenomena finding options for replacing missing wavelengths of light health concerns about the effects of ultraviolet radiation predicting future changes in ultraviolet light output
I gave my students this multiple choice question: In 1879, Marie Cornu discovered that light from the Sun had a drop in ultraviolet (UV) light. Two years later, Walter Hartley found that ozone absorbs certain wavelengths of UV light. What motivated Charles Fabry and Henri Buisson to conduct research that led to the discovery of the ozone layer in the atmosphere of Earth?

Only one answer is correct among these 4 choices:
- inquiring into the causes of observed phenomena
- finding options for replacing missing wavelengths of light
- health concerns about the effects of ultraviolet radiation
- predicting future changes in ultraviolet light output

Could you tell me which one is correct?

inquiring into the causes of observed phenomena