It can be inferred from the passage that crop rotation can increase yields in part because A. moving crop plants around makes them hardier and more resistant to disease B. the number of Pseudomonas fluorescens bacteria in the soil usually increases when crops are rotated C. the roots of many crop plants produce compounds that are antagonistic to phytopathogens harmful to other crop plants D. the presence of phytopathogenic bacteria is responsible for the majority of plant diseases E. phytopathogens typically attack some plant species but find other species to be unsuitable hosts