What is the result of performing R1↔R2R_1 \leftrightarrow R_2R1↔R2 on the matrix (1001)\begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}(1001)?
(0110)\begin{pmatrix} 0 & 1 \\ 1 & 0 \end{pmatrix}(0110)
(1001)\begin{pmatrix} 1 & 0 \\ 0 & 1 \end{pmatrix}(1001)
(0011)\begin{pmatrix} 0 & 0 \\ 1 & 1 \end{pmatrix}(0101)
(1100)\begin{pmatrix} 1 & 1 \\ 0 & 0 \end{pmatrix}(1010)