Which of the Following Is a Valid Spin State $q$ -Vector? (If You Are Using the Letters on the Back

Multiple Choice

Which of the following is a valid spin state $q$ -vector? (If you are using the letters on the back cover, you can indicate more than one choice by pointing to several letters.)

A) $\left[\begin{array}{l}2 \\ -1\end{array}\right]$
B) $\left[\begin{array}{c}-1 / 2 \\ \sqrt{3 / 4}\end{array}\right]$
C) $\left[\begin{array}{l}\frac{1}{3} \\ \frac{2}{3}\end{array}\right]$
D) $\left[\begin{array}{c}\sin ^{2} \frac{1}{2} \theta \\ \cos ^{2} \frac{1}{2} \theta\end{array}\right]$
E) None of the above
F) All of the above