Twenty years ago the Republic of Rosinia produced nearly 100 million tons of potatoes, but last year the harvest bare...

The question reads: Twenty years ago the Republic of Rosinia produced nearly 100 million tons of potatoes, but last year the harvest barely reached 60 million tons. Agricultural researchers, who have failed to develop new higher-yielding strains of potatoes, are to blame for this decrease, since they have been concerned only with their own research and not with the needs of Rosinia. Which one of the following is an assumption on which the argument depends? My immediate anticipation was that the argument was assuming that personal research of the agricultural researches in no way coincided with the needs of Rosinia. Therefore, why not A? Also, note that the answer choices are in a different order on the actual question than they are presented in the "view question" feature of the discussion board. I'm referring to question A on the actual question platform.