A year ago, Dietz foods launched a year long advertising campaign for its canned tuna. Last year Dietz sold 12 millions cans of tuna compared to the 10 million sold during the previous year, an increase directly attributable to new customers brought in by the campaign. Profits from the additional sales, however were substantially less than the cost of the advertising campaign. Clearly, therefore, the campaign did nothing to futher Dietz's economic interests.

Which one if true, most seriously weakens the argument ?

1. Sales of canned tuna account for a relatively small percentage of Dietz Foods' profits.
Irrelevant
2. Most of the people who bought Dietz's canned tuna for the first time as a result of the campaign were already loyal customers of other Dietz products.
Strengthening
3. A less expensive advertising campaign would have brought in significantly fewer new customers for Dietz's canned tuna than did the campaign Deitz foods launchd last year.
This is best choice avaiable. Though unconvincing..
4. Deitz made money on sales of canned tuna last year.
Irrelevant
5. In each of the past 5 years, there was a steep, industry wide decline in sales of canned tuna.
The sales of Dietz foods increased while overall industry is seeing a decline in sales. But we can't attribute their success to the advertising campaign. There might be some other reason.

I believe the correct answer should be E.