A commentator says the campaign guaranteed that participants understood the policy. Which choice most effectively uses the data to…

The commentator's claim is an absolute one, that understanding was guaranteed, and A directly challenges that by reporting the post-campaign figure showing over a third of participants still incorrect or unsure. B reports the pre-campaign baseline, which doesn't address the guarantee claim about the outcome. C is a definitional fact about how the two categories relate, not evidence about the campaign's effectiveness. D is background timing information unrelated to the strength of the claim.