Self-study
All potatoes naturally contain solanine, Support which is poisonous in large quantities. ████████████ ████████ ███████ ████ ████ █████ ███████ ██ █████████ ███ ████ ████ ████████ ███████ █████████ ██████ ██ █████████ █████ ████ ██ ███ ████████ ██ ████████ ██ ████████████ ██ ███ █████ ████████ ███████ ████ ████████ █████ ████ ██ █████ ██ ████ ██ ███ ██ ████████ ████████████ ████████ ██ ███ ████ █████
Summary
For a given size of potato, a peeled wild potato is at least as safe as an unpeeled domesticated potato. Why? Because in any potato, most of the solanine (which is poisonous) is contained in the skin.
Missing Connection
The conclusion draws a comparison between the safety of peeled wild potatoes and unpeeled domesticated potatoes. But the premises only allow us to compare between peeled and unpeeled potatoes of the same kind. (A peeled potato should have less poison than an unpeeled potato of the same kind.)
How to get from premises to conclusion? We need to know how solanine content actually compares between peeled wild potatoes and unpeeled domesticated ones. If we knew that the solanine content that’s left over in a peeled wild potato is no higher than the entire solanine content of a same-size unpeeled domesticated potato, we could reach the conclusion.
9.
Which one of the following, ██ ████████ ██████ ███ ██████████ █████ ██ ██ ████████ ██████
a
The proportion of █ ████████ ████████ ████ ██ █████████ ██ ███ ████ ██ ██████ ██ ████ ████████ ████ ██ ████████████ █████████
This compares proportions, but we need to compare absolute quantities. How much solanine is actually left over in a peeled wild potato, and how does that compare to an unpeeled domesticated one? (A) doesn’t answer either of those questions.
b
The amount of ████████ ████████████ ██ ███ ████ ██ █ ████ ██████ ██ █████ ██████ ██ ██████ ██ ██ ██████████
This only tells us about the poison content of wild potato skin, which is irrelevant. We need to know the amount of solanine left over in a wild potato without skin, and how that compares to the amount in a domesticated potato with skin. (B) ignores both sides of the comparison.
c
There is no ████ ████████ ██ █ ██████ ████ ██████ ████ ██ ██ ████████ ████████████ ██████ ██ ███ ████ █████
This compares the solanine content of a peeled wild potato and a same-size unpeeled domesticated one, and confirms that the wild potato comes in at the same amount of solanine or less. So we can conclude that peeled wild potatoes are indeed at least as safe.
d
There are no █████████ ██████████ ██ ████████████ ████████ █████ ████ █████████
This ignores wild potatoes, so it can’t help us reach the comparison in the conclusion. The fact that solanine is the only poison in domesticated potatoes doesn’t tell us how much poison is in a peeled wild potato, or how that compares to the poison in a domesticated potato.
e
Wild potatoes are █████████ ████ ███████ ████ ████████████ █████████
Irrelevant. The conclusion is only about wild and domesticated potatoes of the same size.