Explanation:

- A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence.
- The total emissive power of a black body is given by the Stefan-Boltzmann law, which states that the total emissive power per unit area is proportional to the fourth power of the absolute temperature of the body.
- In this case, we are given that the total emissive power of the black body is 4.5 kW/m2, but we are not given the temperature of the body.
- However, we can still determine the range of the spectrum in which the wavelength falls based on the total emissive power.
- The wavelength of electromagnetic radiation emitted by a black body is related to its temperature by Wien's displacement law, which states that the wavelength of maximum emission is inversely proportional to the temperature of the body.
- Since we don't know the temperature of the black body, we can't use Wien's displacement law directly. However, we can still make an educated guess based on the total emissive power.
- The total emissive power of a black body is related to its temperature by the Stefan-Boltzmann law, which tells us that the total emissive power per unit area is proportional to the fourth power of the absolute temperature of the body.
- Therefore, if we assume that the temperature of the black body is relatively low (i.e. room temperature or lower), then we can conclude that the wavelength of maximum emission would fall in the infrared region of the spectrum.
- The infrared region of the spectrum is defined as the region of the electromagnetic spectrum with wavelengths longer than those of visible light but shorter than those of microwaves.
- Therefore, we can conclude that the correct answer is option 'D', which states that the wavelength falls in the infrared region of the spectrum.