A graph showing the relative effectiveness of different wavelengths of light in driving photosynthesis is called a/an

Explanation

The correct answer is Option C: Action spectrum. An action spectrum provides a visual representation of the relative effectiveness of different wavelengths of light in driving photosynthesis, making it essential for understanding how various light wavelengths contribute to photosynthesis. Option A, photons, refers to a basic unit of light energy and does not relate to a graph. Option B, Spirogyra, is a type of algae and is unrelated to the graphical representation in question. Accessory pigment, pertains to pigments that capture additional light energy for photosynthesis, not a type of graph.