Which steps are involved in the free-radical mechanism of the bromination of ethane in the presence of ultraviolet radiation?

I.     ${{\text{C}}_2}{{\text{H}}_6} + {\text{Br}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5} \bullet  + {\text{HBr}}$

II.     ${{\text{C}}_2}{{\text{H}}_5} \bullet {\text{B}}{{\text{r}}_2} \to {{\text{C}}_2}{{\text{H}}_5}{\text{Br}} + {\text{Br}} \bullet$

III.     ${{\text{C}}_2}{{\text{H}}_5} \bullet  + {\text{Br}} \bullet  \to {{\text{C}}_2}{{\text{H}}_5}{\text{Br}}$

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

D