D. Few consumers would be willing to pay significantly higher prices for cotton goods than they are now paying.
No impact. They do not need to pay HIGHER price for cotton goods. As long as the consumer pay the CURRENT price of cotton goods, then the plan for the switch will work. Therefore, D is not a weakener.
我加一句,题目中已经说了 “...have caused dramatic increase in the price of cotton on the world market",这个是个既定的事实,说明作者在说这句话之前已经把demand,price等因素已经都考虑到了。因此,任何想要削弱这句话的答案都不对。