Given that,
Temperature, T = 1500 K
Wavelength, 
To find,
The energy of one photon of this light.
Solution,
We know that, the energy of a photon is given by the formula as follows :

So, the required energy is
.
The answer is D; Mercury-194
All of the others are not when I looked them up
Cu = 63.546
N= 14.001 g/mol
O= 15.999 g/mol * 3 = 47.997
Copper (II) Nitrate has a MW of 125.544 g/mol
6.25 x 125.544
= 784.65 <--- is your answer, if there were was a multiple choice or not :)