Which of the following is a 2times22 \\times 22times2 identity matrix?
\\begin{pmatrix} 1 & 0 \\\\ 0 & 1 \\end{pmatrix}
\\begin{pmatrix} 0 & 1 \\\\ 1 & 0 \\end{pmatrix}
\\begin{pmatrix} 1 & 1 \\\\ 1 & 1 \\end{pmatrix}
\\begin{pmatrix} 0 & 0 \\\\ 0 & 0 \\end{pmatrix}