For the reaction ${\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{NO}\left(\mathrm{g}\right),\mathrm{\Delta }H>0$. The concentration of $\mathrm{NO}\left(\mathrm{g}\right)$ in the reaction at equilibrium is increased when

For the reaction ${\mathrm{N}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{NO}\left(\mathrm{g}\right),\mathrm{\Delta }H>0$. The concentration of $\mathrm{NO}\left(\mathrm{g}\right)$ in the reaction at equilibrium is increased when temperature is increased

The equilibrium constant declines in value as the temperature rises. The value of the equilibrium constant rises when the forward reaction is endothermic as the temperature rises.

Hence option A is correct