Which matrix represents the identity transformation in R2R^2R2?
(0110)\begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix}(0110)
(1111)\begin{pmatrix} 1 & 1 \\ 1 & 1 \end{pmatrix}(1111)
(1001)\begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}(1001)
(0000)\begin{pmatrix} 0 & 0 \\ 0 & 0 \end{pmatrix}(0000)