Consider the vectors:
\[
\begin{aligned}
& X_1=\begin{bmatrix} 1 \\ 0 \end{bmatrix}, \quad X_2=\begin{bmatrix} 0 \\ 1 \end{bmatrix}, \quad X_3=\begin{bmatrix} 0 \\ -1 \end{bmatrix}, \\
& X_4=\begin{bmatrix} -1 \\ 0 \end{bmatrix}, \quad X_5=\begin{bmatrix} 2 \\ 2 \end{bmatrix}, \quad X_6=\begin{bmatrix} -2 \\ -2 \end{bmatrix}
\end{aligned}
\]
with corresponding labels:
\[
Y_1=Y_2=Y_5=1, \quad Y_3=Y_4=Y_6=-1
\]
\noindent If a hard margin support vector machine is used, what are the support vectors?
Select the correct option:
- $X_1, X_2, X_5$
- $X_1, X_2, X_3, X_4, X_5, X_6$
- $X_3, X_4$
- $X_1, X_2, X_3, X_4$
