Snowy,
Did you prephrase the main point before this question? I would have done something like this:
Stealing Thunder's effectiveness is supported by 1. widespread belief in the law community, 2. simulated trials (not actual trials), 3. credibility imaging, 4. previewing, 5. scarcity/"old news", 6. framing.
To condense further: "Stealing Thunder's effectiveness is supported by experiment and several psychological theories." or even "Stealing Thunder seems to work."
B and D go against this. A is too strong. C is the only one that omits the limitations. But I don't think that is a problem because that is not really the main point. You could omit all mention of limitations and the thrust would be the same. The evidence for Stealing Thunder is broad but weak. However, the limitations are purely speculative with far less evidence.
"However, it may therefore be effective only when the negative information can be
framed positively."
But this also suggests limitations on the use of the technique:
Only two sentences talk about limitations and they are full of speculation.
It seems you are saying that simulations can demonstrate effectiveness in actual trials, this is not necessarily the case. Also, I think that you did not give enough weight to the word "suggested". Suggesting that something is effective is not equivalent to demonstrating that it is effective.