Where would the electrons in the 3d sublevel be found?
only in the n = 3 energy level
in energy levels > 3
possibly in any shell

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.