Which of the following equation gives the value of heat of formation $\left(\mathrm{\Delta }{H}_f^{\circ }\right)$ ?

 The reaction which provides the value of heat of formation $\left(\mathrm{\Delta }{H}_f^{\circ }\right)$ is,

$\frac{1}{2}{\mathrm{H}}_2\left(\mathrm{g}\right)+\frac{1}{2}{\mathrm{F}}_2\left(\mathrm{g}\right)⟶\mathrm{HF}\left(\mathrm{g}\right)$

This reaction follows the rule of heat of formation.