During which process is there a decrease in the entropy of the system?

A.     ${\text{Ag(s)}} + {\text{2}}{{\text{H}}^ + }{\text{(aq)}} + {\text{NO}}_3^ - {\text{(aq)}} \to {\text{A}}{{\text{g}}^ + }{\text{(aq)}} + {{\text{H}}_2}{\text{O(l)}} + {\text{N}}{{\text{O}}_2}{\text{(g)}}$

B.     ${\text{Ba(OH}}{{\text{)}}_2}{\text{(s)}} \to {\text{BaO(s)}} + {{\text{H}}_2}{\text{O(g)}}$

C.     ${\text{PC}}{{\text{l}}_3}({\text{g)}} + {\text{C}}{{\text{l}}_2}({\text{g)}} \to {\text{PC}}{{\text{l}}_5}({\text{g)}}$

D.     ${{\text{H}}_2}{\text{O(s)}} \to {{\text{H}}_2}{\text{O(l)}}$

C