Happy to help! The questions says, "it can be inferred from the passage that crop rotation can increase yields in part because..."
The part of the passage that discusses crop rotation is in the beginning of the first paragraph in lines 6 through 8, where it states, "The problem can be cured by crop rotation, denying the pathogens a suitable host for a period of time."
We know that crop rotation can deny pathogens a suitable host for some time, so we're looking for an answer choice that states this.
Answer A is incorrect because there is no mention in the passage of crop plants becoming hardier and more resistant to pathogens by moving them around. We can get rid of this choice.
Answer B is incorrect because there is no mention about crop rotating having any effect on P. fluorescens, so we can't infer that the number of this bacterium increases during crop rotation.
Answer C is incorrect because we have no idea what the roots of many crop plants produced, as it isn't mentioned in the passage. Also, even if this answer were true, then why would crop rotating help so much of many plants already have roots with antagonistic properties that fight the pathogens?
Answer D is incorrect because we have absolutely no idea what is responsible for the majority of plant diseases. It's possible that the presence of pathogenic bacteria is only responsible for a small percentage of all plant diseases. We can't infer this answer choice.
Answer E says, "phytopathogens typically attack some planet species but find other species to be unsuitable hosts." This is a paraphrase of what is stated in lines 6 through 8 ("The problem can be cured by crop rotation, denying the pathogens a suitable host for a period of time."), so this is the correct answer.
Does this make sense? Let us know if you have any more questions!
StephJanuary 8, 2019
Yes thank you!
RaviJanuary 9, 2019
@Steph you're welcome!
mjt222April 22, 2020
I'm confused about how the answer is E, because of the use of "species." Isn't the passage saying that within a species some specific plants are unsuitable hosts because of crop rotation, not that different species are unsuitable hosts?
