Answer choice A

Hi @amarachicynthia, Happy to help! The author tells us that cultivating a single crop eventually leads to decreased yields because the levels of harmful bacteria in the soil increase. Even if the crops are not rotated, the severity of the impacts of the harmful bacteria decreases over time. This is because the soil becomes "suppressive." The author then highlights that there may be many reasons for this; however, the levels of certain bacteria in suppressive soil are higher than in non-suppressive soil, suggesting that these bacteria play a role in suppressing harmful bacteria. One example of these bacteria is Pseudomonas fluorescens (PF). Therefore, answer choice (A) is incorrect for two reasons. First, the author notes that there many be many reasons why soil becomes suppressive. Second, PF is only one example of the helpful bacteria. Therefore, the information presented in the passage does not support such a strong conclusion i.e. that PF is the sole cause of soil suppressivity. Answer choice (D) is correct because the author notes that this relationship suggests that helpful bacteria such as PF suppresses harmful bacteria. Therefore, this supports the author's argument that we should research the potential agricultural benefits of genetically altered helpful bacteria. Hope this helps! Please let us know if you have any further questions.

Hi Victoria! Thanks so much for ur reply. I was wondering if you could elaborate on why answer choice E is incorrect? Thanks so much!