Unplugged Practice Test: Logical Reasoning Set 2, Question 11 (Necessary Assumption)
Taking the test? Finish it first. This page shows the answer.
- Necessary Assumption questions ask for the unstated premise the argument depends on.
- Try the negation test. If negating a choice wrecks the argument, that choice is the necessary assumption.
- Every question on this test is original, written to the same logical skeletons as real questions, and Steve checked every one himself before release.
The question
Hydrologist: People who live beside a river cannot prepare sensibly for flooding unless they grasp something of how rivers actually behave. Public understanding of river behavior, though, is bound to be skewed, because most residents form their picture of rivers from televised disaster coverage, which holds an audience by suggesting that a river sits placid for decades and then, with no warning at all, sweeps away everything in its path.
11. The hydrologist's reasoning requires the assumption that
- (A)public understanding of rivers is skewed by the belief that most rivers seldom flood at all
- (B)portraying a river as placid for decades and then suddenly destructive gives a skewed picture of how rivers behave
- (C)most televised coverage of rivers holds its audience by portraying rivers as placid for decades and then suddenly destructive
- (D)any account of a river that is presented as a dramatic story is bound to misrepresent the river
- (E)only accounts prepared without concern for holding an audience can give residents an accurate picture of river behavior
BWhy (B) is correct
The hydrologist argues that public understanding of rivers is skewed because most people get their picture from television coverage showing a river sitting placid for decades, then suddenly sweeping everything away. For that coverage to actually skew understanding, the placid-then-sudden portrayal itself has to be a distorted picture of how rivers behave. (B) supplies exactly that link: negate it, say the portrayal isn't skewed, and the argument collapses.
Why the other answers are wrong
AWhy (A) is wrong
(A) shifts to a belief that rivers seldom flood, a different idea from the placid-then-sudden depiction the hydrologist actually blames.
CWhy (C) is wrong
(C) is a premise restated: coverage draws its audience with that portrayal, which never adds the further point that the portrayal misleads.
DWhy (D) is wrong
(D) reaches too broadly, ruling out every dramatic river account, when the argument only needs this one portrayal to be inaccurate.
EWhy (E) is wrong
(E) demands more than the conclusion requires, that only audience-blind accounts can be accurate.
Common questions
What type of question is this?
Necessary Assumption. Necessary Assumption questions ask for the unstated premise the argument depends on.
How do I get better at Necessary Assumption questions?
Try the negation test. If negating a choice wrecks the argument, that choice is the necessary assumption. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
