Correct option is (A) \(PCl_5 \rightleftharpoons PCl_3 + Cl_2\)
At low pressure, according to the Le Chatelier's principle, reaction will proceed in the direction which has more no. of moles. The number of moles in product side is greater than reactants side. This is the favourable only for the reaction, \(PCl_5 \rightleftharpoons PCl_3 + Cl_2\) among the given reactions. So, that reaction will proceed at low pressure.