If anything, this supports the argument by reinforcing the idea that best-sellers dominated sales over less commercial books. It does not weaken the claim that megastores caused the decline of less commercial books.

This does not weaken the argument because it does not address the cause of the decline in commercial book sales. If anything, it gives more credence to the claim that customers were more attracted to books written by bestsellers.

This undermines one of the author’s key assumptions. If non-commercial books were increasingly printed in paperback, then the decrease in sales of hardcover books could be attributed to a change in format rather than the discounts offered by megastores.

This has nothing to do with the reasoning of the argument. It does address the reasoning for how megastores caused the decline in non-commercial book sales.

This supports the argument because it highlights how megastores prioritize best sellers, which leads to a decrease in sales of noncommercial more literary books.