b) Apple growers have decreased their use of certain pesticides that once were believed to be essential in the prevention of crop destruction, and they were identified by the FDA
I think the problem with B is of pronoun ambiguity. "They" is not clearly referring to the pesticides. Although it is ridiculous to think that "they" would refer to "Apple Growers", but still it does introduce some degree of doubt.
I think the problem with B is of pronoun ambiguity. "They" is not clearly referring to the pesticides. Although it is ridiculous to think that "they" would refer to "Apple Growers", but still it does introduce some degree of doubt.