Hey. I'm not an instructor but I had a similar issue to you when I got to this question. I too have had issues with people responding to questions so I figured that something would be better than nothing. Perhaps A is better because it is explicitly proves the entire process which Steele hypothesized. There is an introduction of a virus, and a change in DNA going into the reproduction cells. Answer E on the other hand doesn't show the process how it happened, perhaps it wasn't a change in DNA. Perhaps it was something else.