Which matrix represents a dilation by factor kkk centered at origin?
\\begin{bmatrix} k & 0 \\\\ 0 & k \\end{bmatrix}
\\begin{bmatrix} 1 & 0 \\\\ 0 & k \\end{bmatrix}
\\begin{bmatrix} k & 0 \\\\ 0 & 1 \\end{bmatrix}
\\begin{bmatrix} 0 & k \\\\ k & 0 \\end{bmatrix}