Let $v$ be a (fixed) unit vector in $\mathbb { R } ^ { 3 }$. (We think of elements of $\mathbb { R } ^ { n }$ as column vectors.) Let $M = I _ { 3 } - 2 v v ^ { t }$. Pick the correct statement(s) from below.\\
(A) $O$ is an eigenvalue of $M$.\\
(B) $M ^ { 2 } = I _ { 3 }$.\\
(C) 1 is an eigenvalue of $M$.\\
(D) The eigenspace for the eigenvalue $-1$ is 2-dimensional.