Which process is endothermic?

A.     ${\text{2}}{{\text{C}}_4}{{\text{H}}_{10}}{\text{(g)}} + {\text{13}}{{\text{O}}_2}{\text{(g)}} \to {\text{8C}}{{\text{O}}_2}{\text{(g)}} + {\text{10}}{{\text{H}}_2}{\text{O(g)}}$

B.     ${\text{Na(g)}} \to {\text{N}}{{\text{a}}^ + }{\text{(g)}} + {{\text{e}}^ - }$

C.     ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}{\text{(aq)}} + {\text{2KOH(aq)}} \to {{\text{K}}_2}{\text{S}}{{\text{O}}_4}{\text{(aq)}} + {\text{2}}{{\text{H}}_2}{\text{O(l)}}$

D.     ${\text{N}}{{\text{H}}_3}{\text{(g)}} \to {\text{N}}{{\text{H}}_3}{\text{(l)}}$

B