Elements have been discovered with up to energy levels.
a. 5
b. 6
c. 7
d. 8

The best answer I think is 7.  If you look at the periodic table, there are 7 periods and each period has a new energy level.  Because of that, I don't think an element can naturally have more than 7 energy levels, however, it might be possible for an electron in the 7th energy level to briefly go up to an exited state due to energy being added.  

The answer to this problem is. 67