In the reaction  $2{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2{\mathrm{SO}}_3\left(\mathrm{g}\right),\mathrm{\Delta }H<0$  The yield of ${\mathrm{SO}}_3\left(\mathrm{g}\right)$ is increased when

In the reaction  $2{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2{\mathrm{SO}}_3\left(\mathrm{g}\right),\mathrm{\Delta }H<0$  The yield of ${\mathrm{SO}}_3\left(\mathrm{g}\right)$ is increased when temperature is decreased and pressure is increased

Sulfur trioxide takes a very long time to develop at low temperatures. Elevating the temperature accelerates the process of reaching equilibrium. On the other hand, a high-temperature results in a lower percentage yield of sulphur trioxide.
The side with the lesser gas volume benefits from an increase in pressure. In the process described above, sulphur dioxide and oxygen combine to generate sulphur trioxide.

Hence option B is correct