Which of these vectors is an eigenvector of A=(3001)A = \begin{pmatrix} 3 & 0 \\ 0 & 1 \end{pmatrix}A=(3001)?
(11)\begin{pmatrix} 1 \\ 1 \end{pmatrix}(11)
(10)\begin{pmatrix} 1 \\ 0 \end{pmatrix}(10)
(12)\begin{pmatrix} 1 \\ 2 \end{pmatrix}(12)
(21)\begin{pmatrix} 2 \\ 1 \end{pmatrix}(21)