Chapter 41.5, Problem 41.5TYU

In which of the following situations is the magnetic moment of an electron perfectly aligned with a magnetic field that points in the positive z-direction? (i) $m_s=+\frac{1}{2}$; (ii) $m_s=-\frac{1}{2}$; (iii) both (i) and (ii); (iv) neither (i) nor (ii).