A Possible Reaction of Ethane with Chlorine Is Shown Below

A possible reaction of ethane with chlorine is shown below. $$\mathrm { CH } _ { 3 } \mathrm { CH } _ { 3 } + \mathrm { Cl } _ { 2 } \longrightarrow \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { Cl } + \mathrm { HCl }$$ This reaction could conceivably occur by the following chain mechanisms [1], [2], and [3]. The chain propagating step(s) is (are) _______. $[ 1 ] \quad \mathrm { Cl } _ { 2 } \longrightarrow 2 \mathrm { Cl } \cdot$
[2] $\mathrm { Cl } \cdot + \mathrm { CH } _ { 3 } \mathrm { CH } _ { 3 } \stackrel { \text { slow } } { \longrightarrow } \mathrm { HCl } + \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 }^ \cdot$
[3] $\mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } ^\cdot + \mathrm { Cl } _ { 2 } \stackrel { \text { fast } } { \longrightarrow } \mathrm { CH } _ { 3 } \mathrm { CH } _ { 2 } \mathrm { Cl } + \mathrm { Cl }\cdot$ .

A) Only [1] and [2]
B) Only [2] and [3]
C) Only [1] and [3]
D) Only [3]