Nevermind, i figured it out on my own. The question had little or nothing to do with the bond energies, b/c 4 of the 5 choices are propagation steps and only 1 is a termination step. B/c the amount of free radicals available to react is significantly lower in a termination step to a free radical reaction, the probability that a termination reaction will occur is much less than the probability that a propagation reaction will occur. So obvious answer D. You guys were so helpful!! Thanks, I couldn't have done it without your h elp!! What a joke.