This is a weaken question. Kyle's argument addresses only half of Sajitha's claim. She points out the effect of the new label and new ads. He responds only to the claim about the new ads, showing why the ads probably didn't cause the first part of the increase in sales. An obvious weak point of his response, then, is that the new label may have had the effect Sajitha claimed it did. Consider each choice in turn:

(A) This doesn't limit the effectiveness of Kyle's claim, which points out that the ads wouldn't have caused a sales increase in early 2000.
(B) This choice suggests an external cause of the sales increase, but it isn't strictly within the scope of Kyle and Sajitha's dispute. A better choice would have to do with something Sajitha's claim implied.
(C) By focusing on the advertising campaign, this choice doesn't affect the validity of Kyle's response.
(D) Experimentation may benefit or not benefit Lodgewood. Like (B), it's an external cause to the dispute between Kyle and Sajitha.
(E) This is correct. We're looking for something having to do with the new label, and this choice gives us a reason why, in line with Sajitha's claim, the data shows a rise starting in early 2000.