Which of the following matrices is nilpotent?
(0500)\begin{pmatrix} 0 & 5 \\ 0 & 0 \end{pmatrix}(0050)
(1000)\begin{pmatrix} 1 & 0 \\ 0 & 0 \end{pmatrix}(1000)
(0110)\begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix}(0110)
(2002)\begin{pmatrix} 2 & 0 \\ 0 & 2 \end{pmatrix}(2002)