Which of the following statements regarding free radical halogenation of alkane is not true? 

• A

   Hydrogen abstraction by halogen radical in the propagation step is  exothermic in both chlorination and bromination.  

• B

   Hydrogen abstraction by halogen radical in propagation step is  exothermic in chlorination but endothermic in bromination.

• C

  A single halogen radical may bring about halogenation of thousands of alkane molecules

• D

  Continuous source of energy is required to continue the free radical halogenation reaction.