It’s unclear whether the ad campaign was created by the “competing consultant.” Even if it was the competitor’s campaign and the consultant did assume this, (A) fails to point out that LRG’s low sales might have been caused by something other than the campaign.

The consultant fails to consider that LRG’s low sales might have been caused by something other than the ad campaign, like economic changes.

The consultant points out that LRG’s new products are selling especially poorly this year, but he never assumes that the new products should outsell older, more established products. Even if he did, (C) doesn’t address the fact that something else might have caused the low sales.

The consultant points out that new product sales are especially low, but he never makes any assumptions about why established product sales are higher. Instead, he assumes that low sales overall are due to the ineffective ad campaign.

This is the cookie-cutter flaw of confusing sufficient and necessary conditions. The consultant doesn’t make this mistake; his argument relies on causal logic, not conditional logic.