Q17

[peg_city]

Why is C right when it says that yields increase 27% on line 21?

Thanks

[giladedelman]

Thanks for posting.

You're missing something here. We know that PF bacteria improves crop yields by suppressing harmful phytopathogens. But this question is asking us about crops that are impervious to phytopathogens. Well, if they're impervious, then there's probably no benefit to be gained from adding PF to the soil, since they already are not being harmed by the phytopathogens. We would only expect an increase in yield for plants that are harmed by these parasites.

To take a real-world example: mosquito repellent reduces itchy bug bites. But I already don't get bitten by mosquitoes (don't ask me why). So spraying mosquito repellent on me wouldn't likely reduce my bug bite total, since I'm already not being bitten.

That's why (C) is right.

(A) is incorrect because although PF wouldn't help these crops, it could still be there -- we don't know.

(B) is likewise unsupported; we don't know whether they would crowd out other plants.

(D) is out because we don't really have any information about how fast plants mature.

(E) is also unsupported; if anything, I would kind of expect the opposite: I'd expect fewer phytopathogens surrounding the plants that are impervious to them (just like I'd expect fewer mosquitoes buzzing around me).

Does that answer your question?