Assumption is an unstated premise. It is a must statement for the conclusion to be hold true.
Here option E talks about rates of the magazine. Now it is not necessary for the rates to be three times. It can be any. We can't conclude based on rates that the sale is high.
Choice B tells us that the final authority lies with the publisher. Now if we negate this, 'The final authority does not lies with the publisher' then the conclusion does not hold true. Hence, this statement need to be right for the conclusion. That's why it is an answer.
bbz789 wrote:
Why is the answer B? Should E fit better since the opponents suggested that the new publisher is more interested in boosting sales?