CEO: While we only have the sales reports for the first 9 months of this year, I feel confident in concluding that th...

@Mehran I am a little confused as to why answer A strengthens the argument here. I was between A and D but ultimately chose D. The answer explanation helped a lot in framing the question, but I am still confused about this question conceptually. In the errors in reasoning lesson, we learned that past success cannot guarantee future success and that concluding something will happen because it has happened before is a logical flaw. When we add answer A to the evidence, the paraphrased argument looks like: "I feel confident that this will be a good year because our typical sales avg. is less than $30m/yr and it is currently $35 m/yr in the first 9 months this year. Also, our company typically has its highest sales in the last few months." While I see that this addresses the gap regarding the last three months, doesn't it do this on questionable grounds? Can we strengthen an argument even when the new evidence makes the argument suspect on new grounds? Am I wrong in thinking that adding this evidence merely adds flawed evidence as the basis for the conclusion? Answer D does fail to address the last three month period, but it provides a cause for their success ($35m/yr) relative to other years. Paraphrased, this argument would read: "I feel confident that this will be a good year because our typical sales avg. is less than $30m/yr and it is currently $35 m/yr in the first 9 months this year. Also, our new advertising campaign implemented this year has proved to be unusually effective thus far." While there is still a hole in the argument regarding the last three months, this seems to strengthen the argument by providing a reason (unusually effective ads) for the conclusion (confidence that this will be a good year in sales). Strengthening questions do not require that we make the argument airtight, but rather the conclusion more likely. In A, it seems like we are adding flawed evidence that addresses the central gap in the argument's logic (i.e. the last three months), whereas in D we are providing a cause for why the company is experiencing such success, which seems to strengthen the argument, though it fails to touch on the last three months of the year. Any insight you can provide here would be very helpful. Thanks!