Which equation represents a propagation step in the mechanism for the reaction between ethane, ${{\text{C}}_{\text{2}}}{{\text{H}}_{\text{6}}}$, and chlorine, ${\text{C}}{{\text{l}}_{\text{2}}}$, in the presence of sunlight/UV?

A.     ${{\text{C}}_2}{{\text{H}}_6} + {\text{Cl}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5} \bullet  + {\text{HCl}}$

B.     ${{\text{C}}_2}{{\text{H}}_6} + {\text{Cl}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5}{\text{Cl}} + {\text{H}} \bullet$

C.     ${\text{C}}{{\text{l}}_{\text{2}}} \to 2{\text{Cl}} \bullet$

D.     ${{\text{C}}_2}{{\text{H}}_5} \bullet  + {\text{Cl}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5}{\text{Cl}}$

A