Correct Option: A

Wavelength of light between 400 nm and 700 nm is most effective for photosynthesis. This light is called photosynthetically active radiation (PAR). Comparatively more photosynthesis occurs is red and blue regions though others have significant net photosynthesis. Light has maximum efficiency in red and minimum in blue region. In both these regions light is absorbed by chlorophyll. Red light favours more carbohydrate accumulation while blue light favours more protein synthesis.