Final answer:
The wavelength best absorbed by chlorophyll b is 450 nm, corresponding to the blue light that is most effective for photosynthesis in plants with this pigment. Therefore, the most appropriate correct option is B.
Step-by-step explanation:
The wavelength of light best absorbed by chlorophyll b is in the range of 450 nm, which corresponds to blue light on the visible spectrum according to the information provided on the absorption spectrum. This is also the strongest peak for chlorophyll b absorption, making it the most efficient wavelength for photosynthesis in plants containing this pigment. In the scenario given, where plants containing only chlorophyll b are exposed to different wavelengths, they would harness the most energy for photosynthesis from radiation at 450 nm.