Which change will favour the reverse reaction in the equilibrium?

$${\text{2CrO}}_{\text{4}}^{2 - }{\text{(aq)}} + {\text{2}}{{\text{H}}^ + }{\text{(aq)}} \rightleftharpoons {\text{C}}{{\text{r}}_{\text{2}}}{\text{O}}_{\text{7}}^{2 - }{\text{(aq)}} + {{\text{H}}_{\text{2}}}{\text{O(l)}}\;\;\;\;\;\Delta H =  - {\text{42 kJ}}$$

A.     Adding ${\text{O}}{{\text{H}}^ - }{\text{(aq)}}$

B.     Adding ${{\text{H}}^ + }{\text{(aq)}}$

C.     Increasing the concentration of ${\text{CrO}}_{\text{4}}^{2 - }{\text{(aq)}}$

D.     Decreasing the temperature of the solution

A