PrepTest 105, Section 1, Question 9

What we’re looking for

Working the answers

• A

  A larger fraction removed still might leave a larger amount behind. Change the wild potato in our example to 70 units in the skin and 30 inside. Its skin now holds 70 percent of its solanine, versus 60 percent for the domesticated potato. A is true, yet peeling the wild potato leaves 30 units compared with the domesticated potato's total of 10. The comparison still fails.

• B

  This tells us the skin contains enough poison to be dangerous. It doesn't tell us how much remains after we remove it. There could be a poisonous amount in the skin and another poisonous amount inside. Nor does B compare that remaining amount with the domesticated potato's total.

• C
  Correct

  This supplies the amount comparison the argument was missing. After peeling, the wild potato has no more solanine than the whole domesticated potato of the same size. On the solanine-based safety comparison developed in the passage, that lets us make the claimed comparison. The amount could be equal or lower; either satisfies “no more.”

• D

  Ruling out other poisons in domesticated potatoes doesn't tell us how much solanine remains in the wild potato after peeling. Even if D is true, our example can still leave 40 units in the wild potato compared with 10 in the domesticated one. The identified gap remains.

• E

  The conclusion explicitly compares potatoes of the same size. What size wild potatoes generally reach doesn't settle that comparison. And smaller size alone wouldn't establish a lower amount of solanine anyway. We need the amount after peeling, not a general statement about size.