12. The Pauli-X matrix, denoted by $\hat{\sigma}_x$, is represented as $$ \hat {\sigma} _ {x} = \left( \begin{array}{c c} 0 & 1 \\ 1 & 0 \end{array} \right). $$ Find the expectation value $\langle \hat{\sigma}_x\rangle$ in the spin state: $$ | \psi \rangle = \alpha_ {+} \left( \begin{array}{c} 1 \\ 0 \end{array} \right) + \alpha_ {-} \left( \begin{array}{c} 0 \\ 1 \end{array} \right), $$ where $\alpha_{+}$ and $\alpha_{-}$ are complex numbers. (A) 0 (B) $2\operatorname{Re}(\alpha_{+}^{*}\alpha_{-})$ (C) $2\operatorname{Im}(\alpha_{+}^{*}\alpha_{-})$ (D) $|\alpha_{+}|^{2} - |\alpha_{-}|^{2}$ (E) $|\alpha_{+}|^{2} + |\alpha_{-}|^{2}$