Critical Reasoning

A year ago, Dietz Foods launched a yearlong
advertising campaign for its canned tuna. Last year
Dietz sold 12 million 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 further Dietz's economic interests.
Which of the following, if true, most seriously weakens
the argument?
(A) Sales of canned tuna account for a relatively
small percentage of Dietz Foods' profits.
(B) 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.
(C) A less expensive advertising campaign would
have brought in significantly fewer new
customers for Dietz's canned tuna than did the
campaign Dietz Foods launched last year.
(D) Dietz made money on sales of canned tuna last
year.
(E) In each of the past five years, there was a steep,
industry-wide decline in sales of canned tuna.

It has to be between C and E..
Conclusion: the ad campaign did nothing to to further economic interests.
Option should show that no..the increase in sale was due to the ad campaign..
[spoiler]C->[/spoiler] if cheaper ad campaign should have been there..then fewer customers would have been there and hence the expensive ad had more customers and hence sales of canned tuna increased... => The argument about ad campaign did very little to further economic interests is weakened..
[spoiler]E-> [/spoiler]Everyone experienced sales decline but Dietz experienced increase in sales...So, this increase in sales could be attributed to the ad campaign... => The argument about ad campaign did very little to further economic interests is weakened..

Now...which one to chose...
Btw OA is E