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Command of evidence practice

SAT, PSAT and ACT Information and Ideas · 56 questions in the bank

These questions state a claim, a hypothesis or a conclusion, and ask which piece of evidence would most directly support it. Sometimes the evidence is a quotation, sometimes it is a finding from a study.

The difficulty is never the reading. It is that three of the four options are genuinely related to the topic, and only one of them actually does the job the question asked for.

How to answer these

  1. Restate the claim in your own words before looking at any option. If you cannot say it simply, you will not be able to test anything against it.
  2. Identify what would have to be true for the claim to hold. That turns a vague 'supports' into something you can check.
  3. Test each option against that specific requirement. Ask: does this make the claim more likely, or is it merely about the same subject?
  4. Watch the scope. Evidence about one site cannot support a claim about all sites, and evidence about a correlation cannot support a claim about a cause.

What the wrong answers look like

Practice questions

Four real questions from the CruxStudy bank, with the keyed answer marked and the explanation behind a click so you can try them first.

Example 1Easier
Ornithologist Maya Chen hypothesizes that young zebra finches learn their songs not merely by listening to adult males but by receiving social feedback while they practice. In her view, a juvenile that sings in the presence of an attentive adult should develop a more accurate copy of the adult song than a juvenile that hears the same song the same number of times without any social interaction.

Which finding, if true, would most directly support Chen's hypothesis?

  1. Juveniles that practiced near adults who reacted to their singing reproduced the adult song more accurately than juveniles that heard identical songs played from a speaker. correct
  2. Juveniles raised in complete silence, with no adult song audible at any point during their first three months, developed songs that were abnormal in overall structure and unusually short.
  3. Adult male zebra finches sing more frequently in spring than at other times of year, and juveniles hatched in spring therefore hear a greater total number of songs.
  4. Juveniles tended to copy whichever adult song was loudest in the aviary, regardless of whether the adult producing it responded to their practice attempts at all.
Show the explanation

A supporting finding has to test Chen's specific claim that social feedback beats mere exposure, and the option comparing juveniles who practiced near reacting adults with juveniles who heard identical songs from a speaker makes exactly that comparison. Juveniles raised in complete silence with no adult song audible shows only that hearing song matters, which does not distinguish social feedback from passive listening. Adult males singing more frequently in spring so that spring-hatched juveniles hear more songs concerns seasonality and sheer exposure rather than feedback, and copying whichever song was loudest regardless of whether the adult responded points away from interaction altogether.

Example 2Medium
Biologists studying tomato plants observed that when caterpillars chew on one plant, nearby undamaged plants begin producing defensive compounds within hours. The team claims that airborne chemicals released by the damaged plant travel to its neighbors and trigger their defenses.

Which finding, if true, would most directly weaken the team's claim?

  1. The defensive compounds deter caterpillars from feeding in laboratory tests, and plants carrying higher concentrations of them lose less leaf tissue over a season.
  2. Damaged tomato plants begin releasing airborne chemicals within minutes of an attack, well before neighboring plants show any measurable change in their own chemistry.
  3. Several other plant species, including sagebrush and wild lima bean, release airborne chemicals of a similar kind when their leaves are chewed by insects.
  4. Neighboring plants produced the same defensive compounds even when the damaged plant's airborne chemicals were blocked from reaching them. correct
Show the explanation

To weaken the claim, a finding must break the link between the airborne chemicals and the neighbors' response, and neighbors producing the same defensive compounds while those chemicals were blocked does exactly that. Damaged plants releasing airborne chemicals within minutes, before neighbors change, is tempting because it involves the chemicals, but that timing fits the team's claim rather than contradicting it. The compounds deterring caterpillars and reducing leaf loss, and sagebrush and wild lima bean releasing similar chemicals, both leave the claimed signaling mechanism untouched.

Example 3Harder
A midsize city eliminated bus fares at the start of 2022, and ridership rose 30 percent within a year. Transit officials concluded that removing fares caused the increase, arguing that ticket cost had been the main barrier keeping residents off buses.

Which finding, if true, would most directly weaken the officials' conclusion?

  1. Bus ridership in a neighboring city that kept its fares remained flat over the same year.
  2. At the start of 2022, the city also doubled the frequency of buses on its busiest routes. correct
  3. In surveys conducted before 2022, many residents cited cost as a reason they avoided the bus.
  4. The fare-free program cost the city more than officials had originally projected.
Show the explanation

Doubling service frequency at the same time introduces a rival explanation for the ridership increase, so the officials cannot attribute it to free fares alone. The first and third choices actually support the conclusion, and the program's cost is irrelevant to what caused ridership to rise.

Example 4Medium
Historians have debated when the fortified wall around the ancient city of Karsuna was built. One group argues that construction began shortly after a devastating raid recorded in clay tablets dating to about 1200 BCE, making the wall a direct response to that attack.

Which finding, if true, would most directly support the group's argument?

  1. The clay tablets describe raids on several other cities in the same period.
  2. The wall shows evidence of having been repaired many times over the centuries, with at least four distinct phases of masonry visible in its northern section.
  3. Cities that were never raided sometimes built similar fortified walls.
  4. Tree-ring dating shows that timbers embedded in the wall's foundation were felled within a decade after 1200 BCE. correct
Show the explanation

Foundation timbers cut just after 1200 BCE place the start of construction right after the recorded raid, exactly the timing the group proposes. Repairs in at least four distinct phases of masonry establish only that the wall was maintained for a long time, not when it was first raised. The clay tablets describing raids on several other cities in the same period say nothing about Karsuna's wall, and cities that were never raided building similar walls would if anything weaken the link between the raid and the construction.

Drill all 56 of them

Open the drill inside CruxStudy and it serves command of evidence questions one at a time, with an explanation after every answer and your accuracy tracked. Free, no account.

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Common questions

What is a command of evidence question?

A question that states a claim and asks which quotation or finding would most directly support, weaken or illustrate it.

How do I avoid the on-topic trap?

Restate the claim first, then ask of each option whether it makes that exact claim more likely. Being about the right subject is not the same as being evidence for it.

Are these questions on the ACT?

ACT Reading asks closely related questions about what the passage supports, though it does not use the same label.

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