Which of the following matrices is already in diagonal form?
(1002)\begin{pmatrix} 1 & 0 \\ 0 & 2 \end{pmatrix}(1002)
(1102)\begin{pmatrix} 1 & 1 \\ 0 & 2 \end{pmatrix}(1012)
(0110)\begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix}(0110)
(2222)\begin{pmatrix} 2 & 2 \\ 2 & 2 \end{pmatrix}(2222)