Which of the Following Reactions Would Have an Activation Energy $\rightarrow$

Which of the following reactions would have an activation energy equal to zero?

A) H-H $\rightarrow$ 2H·
B) H· + CH₃-H $\rightarrow$ CH₃--H + H·
C) CH₃· + CH₃· $\rightarrow$ CH₃-CH₃
D) CH₃· + CH₃-H $\rightarrow$ CH₃-H + CH₃·
E) All of the above