Consider the following equation:

$2{\mathrm{SO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\rightleftharpoons 2{\mathrm{SO}}_3\left(\mathrm{g}\right),\mathrm{\Delta H}=-190 \mathrm{kJ}$.

The number of factors which will increase the yield of ${\mathrm{SO}}_3$ at equilibrium from the following is _____ .

A. Increasing temperature
B. Increasing pressure
C. Adding more ${\mathrm{SO}}_2$
D. Adding more ${\mathrm{O}}_2$
E. Addition of catalyst

The given reaction is exothermic reaction, hence, decreasing temperature is the favourable condition. The change in gaseous moles of products and reactants is negative, hence, increasing pressure is the favourable condition. Addition of reactants and removal of products are the favourable conditions. Catalyst only increase the speed of the reaction.

The yield of ${\mathrm{SO}}_3$ at equilibrium will be due to :
B. Increasing pressure
C. Adding more ${\mathrm{SO}}_2$
D. Adding more ${\mathrm{O}}_2$