The correct option is C 660-700 nm
Photosynthesis is the ability of plants to absorb the light energy in the form of sunlight, and convert it into chemical energy that can be used as fuel for the plant activities. To do this, plants have pigment molecules such as chlorophyll. These pigments absorb energy from red light effectively. Therefore the most effective wavelength of light for photosynthesis is in the red region of the visible spectra or between 660 – 700 nm.