Which change will decrease the rate of the reaction between ${\mathrm{I}}_2\left(\mathrm{s}\right)$ and ${\mathrm{H}}_2\left(\mathrm{g}\right)$?

Heating the reaction mixture

Increasing the partial pressure of ${\mathrm{H}}_2\left(\mathrm{g}\right)$

Adding a catalyst for the reaction

Adding the l2 (s) as one piece rather than as several small ones