MartyMurray
Deep tillage is even more deleterious to the world's topsoil supply than previously believed. For example, farmers who till deeply are ten times more likely to lose topsoil to erosion than are farmers who use no-till methods. Results like these make it clear that farmers who now till deeply should strive, by using other topsoil aeration techniques, to incorporate no-till methods instead.
The main conclusion of the argument is the following:
farmers who now till deeply should strive, by using other topsoil aeration techniques, to incorporate no-till methods instead
The main conclusion is supported by the following intermediate conclusion:
Deep tillage is even more deleterious to the world's topsoil supply than previously believed.
which is suppported by the following example:
For example, farmers who till deeply are ten times more likely to lose topsoil to erosion than are farmers who use no-till methods.
We see that the author of the argument has observed a correlation between deep tillage and increased topsoli erosion, "farmers who till deeply are ten times more likely to lose topsoil," and concluded, essentially, that deep tillage causes increased topsoil erosion and therefore should be replaced with no-till methods.
The argument depends on assuming which one of the following?
This is an Assumption question, and the correct answer will state an assumption necessary for the premise to support the conclusion.
(A) Topsoil erosion does not make farmers want to till more deeply.
This choice is interesting.
After all, if this choice is not true, then the following is the case:
Topsoil erosion makes farmers want to till more deeply.
In that case, it could be that the reason why there's more topsoil erosion where farmers till deeply is not that tilling deeply causes erosion but rather that erosion causes tilling deeply.
Of course, in that case, the support the evidence provides for the conclusion is severely weakened because it could be that, even though the evidence is true, the conclusion is not. In other words, if this choice is not true, the argument doesn't work.
So, the argument depends on assuming that this choice is true.
Keep.
(B) In deep-tillage farming, the deeper one tills, the greater the susceptibility to topsoil erosion.
The argument does not involve any claims about the effects of tillling deeper.
Also, regardless of whether this choice is true, it remains the case that more soil erosion occurred when deep tilling was done, and that evidence supports the conclusion.
So, this argument doesn't depend on this choice.
Eliminate.
(C) Tilling by any method other than deep tillage is not a viable option.
Regardless of whether this choice is true, farmers can prevent soil erosion by using no-till methods. In other words, even if there is another viable tilling method, it could still be the case that using no-till methods is the best option and thus the one farmers "should strive ... to incorporate."
So, the argument works regardless of whether this choice is true.
Eliminate.
(D) The most expensive farming methods employ topsoil aeration techniques other than deep tillage.
If anything, this choice is a reason to use deep tillage to minimize expense.
Since the author is arguing for ceasing to use deep tillage, if anything, this choice goes against the argument.
Eliminate.
(E) On average, topsoil that is no-tilled is more aerated than topsoil that is tilled deeply.
The conclusion of the argument is not about using no-till methods to achieve more aeration. It's about using no-till methods to prevent erosion.
So, regardless of whether this choice is true, the argument works.
Eliminate.
Correct answer: A
I also marked A, why OA given is C?