Answer:
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First we find the energy level with the following formula, where a is the energy level, n1 is the final energy level, n2 is the starting energy level and r is Rydberg's constant in Joules

We insert the values


The wavelength is found with this formula, where h is Planck's constant and c is the speed of light

Finally we insert the values

Which is the same as 93.8 nm
Mechanics is dealing with forces that are effecting some body, electrostatics is about electrical fields of not moving bodies, and quantum mechanics is dealing with quantum states of atoms.
Thermodynamics as the word say, is dealing with thermal energy that is moving (transferring from one body to another or even better from one medium to another).
Answer is C <span />