Which equation represents a propagation step in the free-radical chlorination of ethane?
CH3CH3+Cl∙→CH3CH2Cl+H∙\text{CH}_3\text{CH}_3 + \text{Cl}^\bullet \to \text{CH}_3\text{CH}_2\text{Cl} + \text{H}^\bulletCH3CH3+Cl∙→CH3CH2Cl+H∙
CH3CH2∙+Cl2→CH3CH2Cl+Cl∙\text{CH}_3\text{CH}_2^\bullet + \text{Cl}_2 \to \text{CH}_3\text{CH}_2\text{Cl} + \text{Cl}^\bulletCH3CH2∙+Cl2→CH3CH2Cl+Cl∙
CH3CH2∙+Cl∙→CH3CH2Cl\text{CH}_3\text{CH}_2^\bullet + \text{Cl}^\bullet \to \text{CH}_3\text{CH}_2\text{Cl}CH3CH2∙+Cl∙→CH3CH2Cl
CH3CH3+Cl2→CH3CH2Cl+HCl\text{CH}_3\text{CH}_3 + \text{Cl}_2 \to \text{CH}_3\text{CH}_2\text{Cl} + \text{HCl}CH3CH3+Cl2→CH3CH2Cl+HCl