$\begin{array}{cc}\mathrm{x}& \mathrm{z}\end{array}$

$\begin{array}{c}\mathrm{x}\\ \mathrm{y}\\ \mathrm{z}\end{array}$

$\begin{array}{c}\mathrm{x}\\ \mathrm{z}\end{array}$

$\begin{array}{cc}\mathrm{x}& \mathrm{w}\\ \mathrm{y}\\ \mathrm{z}\end{array}$