The correct option is C Green light
Photosynthesis is defined as a process that is carried out by the plants and some other organisms to convert light energy from the sun into chemical energy that is released to fuel the organisms activities. It is made up of two different reactions, light dependent and light independent. The pigment chlorophyll is the main light absorbing pigment in all organisms. However, not all wavelengths of light support photosynthesis and the photosynthetic spectrum depends on the type of accessory pigments present in the organism. The non-absorbed part of the light spectrum which gives the organism its color is the least effective in photosynthesis hence green light is the least effective one.