So we want to know what does the wavelength of vidible light corresponds to. So the wavelength of visible light is around 400 - 700 nm or 400*10^-9 m to 700*10^-9 m. Virus size is around 20 - 400 nm. Large moleculer are around 100 nm to 200 nm. Atoms are around 10^-10 m and all the other options are too large. So the correct answer is B.
