Which Statement Is True of Bohr's Equation, E = -B/n²

Multiple Choice

Which statement is true of Bohr's equation, E = -b/n²?

A) E represents the energy of the proton.
B) b represents the energy of an excited electron.
C) The negative sign in the equation suggests that any electron with a finite value of n has a lower energy than an unbound electron.
D) The possible values of n are any real number
E) Each orbit is identified by its unique values for b and n.