The radical chain reaction of ethane with chlorine proceeds via a free radical mechanism. Which of the following represents the correct chain propagation steps?

• A
  $(i) \dot{Cl} + CH_3-CH_3 \rightarrow CH_3-C\dot{H}_2 + HCl$
  $(ii) CH_3-C\dot{H}_2 + Cl_2 \rightarrow CH_3-CH_2Cl + \dot{Cl}$
• B
  $(i) \dot{Cl} + CH_3-CH_3 \rightarrow CH_3\dot{Cl} + C\dot{H}_3$
  $(ii) C\dot{H}_3 + Cl_2 \rightarrow CH_3\dot{Cl} + \dot{Cl}$
• C
  $(i) \dot{Cl} + CH_3-CH_3 \rightarrow CH_3-CH_2-Cl + \dot{Cl}$
  $(ii) \dot{H} + Cl_2 \rightarrow HCl + \dot{Cl}$
• D
  $(i) CH_3-C\dot{H}_2 + Cl-Cl \rightarrow CH_3-Cl + \dot{Cl}$
  $(ii) Cl-CH_3 + CH_3-CH_3 \rightarrow CH_3-C\dot{H}_2 + \dot{Cl}$