An Alternate Mechanism for the Chlorination of Methane Is: Cl₂ $\rightarrow$

An alternate mechanism for the chlorination of methane is: Cl₂ $\rightarrow$ 2Cl·
Cl-Cl, $\Delta$ H° = 243 kJ mol^-1
Cl· + CH₄ $\rightarrow$ CH₃Cl + H·
CH₃-H, $\Delta$ H° = 440 kJ mol^-1
H· + Cl₂ $\rightarrow$ HCl + Cl·
CH₃-Cl, $\Delta$ H° = 352 kJ mol^-1
H-Cl, $\Delta$ H° = 432 kJ mol ^-1
This mechanism is unlikely because:

A) The overall $\Delta$ H° is highly endothermic.
B) The probability factor is low.
C) One of the chain propagating steps is non-productive.
D) One of the chain propagating steps has a very high E_act.
E) One of the chain propagating steps is highly exothermic.