$$Extensible Hypertext Markup Language $($XHTML$)$ version $\_\_\_\_\_$ is an update to HTML $4\mathrm{.}01$ that provides support for a variety of new features including semantic page elements, column layout, form validation, offline storage, and enhanced multimedia.

a$.$

$1\mathrm{.}1$

b$.$

$5\mathrm{.}0$

c$.$

$2\mathrm{.}0$

d$.$

$1\mathrm{.}0$