Bad Qubits — Learn Quantum by Doing

Multiple choice

The average occupation of a single-particle level of energy epsilon is n_BE = 1/(e^((epsilon-mu)/kT) - 1) for bosons and n_FD = 1/(e^((epsilon-mu)/kT) + 1) for fermions. What is the only difference between the two distributions, and what does it enforce for fermions?

A factor of 2 in the numerator for fermions, accounting for spin degeneracy
The sign in the denominator (-1 for bosons, +1 for fermions); the +1 guarantees n_FD <= 1, i.e. the Pauli principle
Bose-Einstein uses kT while Fermi-Dirac uses 2kT in the exponent
The sign of the exponent; it makes fermion occupations grow without bound