Which transformation matrix represents a shear in the x-direction?
(1k01)\begin{pmatrix} 1 & k \\ 0 & 1 \end{pmatrix}(10k1)
(10k1)\begin{pmatrix} 1 & 0 \\ k & 1 \end{pmatrix}(1k01)
(k110)\begin{pmatrix} k & 1 \\ 1 & 0 \end{pmatrix}(k110)
(100k)\begin{pmatrix} 1 & 0 \\ 0 & k \end{pmatrix}(100k)