Drill 18 · Reading & Writing · Hard Command of Evidence
SAT Reading & Writing: Hard Command of Evidence (Drill 18) is a Reading & Writing practice drill covering Hard Command of Evidence. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
Five hard Command of Evidence questions on unfamiliar subjects, anchored by two data displays. Expect wrong choices that are accurate in isolation yet sidestep the precise comparison the argument needs. Each table and graph rewards reading for one specific contrast rather than the largest or smallest number on the page.
Trapped Dust in Four Slices of an Ice Core
| Core slice | Centuries it spans | Total dust (units) |
|---|---|---|
| Slice 1 | 2 | 40 |
| Slice 2 | 5 | 75 |
| Slice 3 | 1 | 35 |
| Slice 4 | 4 | 60 |
Each slice of the ice core holds dust that settled over a different number of centuries. A team wanted to find the dustiest climate, meaning the slice that trapped the most dust per century, not merely the largest pile overall. Because the slices cover unequal spans, the team cautioned that the slice with the largest total need not be the dustiest per century. Comparing the dust each slice trapped for every century it spans, the team concluded that the dustiest interval was ________
Question 1. Which choice most effectively uses data from the table to complete the statement?
Explanation: Choice A is the best answer because the dustiest interval is the one with the most dust per century, so each total must be divided by the centuries it covers. That gives twenty, fifteen, thirty-five, and fifteen units per century for the four slices, so Slice 3, at thirty-five per century, is dustiest even though its total is far from the largest. Choice B is wrong because Slice 2 does hold the largest total, but spread over five centuries it averages only fifteen units per century, among the lowest rates, so the largest pile is not the dustiest climate. Choice C is wrong because Slice 4's sixty units over four centuries work out to fifteen per century, below Slice 3's rate, so its middling total does not make it dustiest. Choice D is wrong because how many centuries Slice 1 spans is true from the table but does not by itself identify the highest dust rate, which requires comparing dust per century.
Ancient plant remains and even wooden objects emerge from certain peat bogs in remarkable condition. One researcher proposed that the bogs' strong acidity is what halts decay, by stopping the microbes that would otherwise break the material down. A rival idea held that it is simply the waterlogged, airless conditions, common to such bogs, that do the preserving.
Question 2. Which finding, if true, would most help distinguish between the two explanations?
Explanation: Choice B is the best answer because the two explanations split on whether acidity or mere waterlogging does the preserving, so the deciding evidence holds waterlogging constant and varies acidity. Among equally waterlogged bogs, only the acidic ones preserving remains well shows acidity is the active factor, not the airless water the rival points to. Choice A is wrong because bogs preserving wood better than dry soil contrasts bogs with non-bogs but does not separate acidity from waterlogging, since bogs have both. Choice C is wrong because the mosses that grow on acidic bogs describe their ecology, not what halts decay in the peat. Choice D is wrong because the brown staining shows the peat colors what it holds but says nothing about which condition stops the material from decaying.
Two early printed books carry no printer's name, and historians dispute whether the same workshop produced both. One scholar argued that a single workshop printed them. A skeptic replied that the resemblance could be superficial, since many early workshops imitated one another's styles, and a shared look need not mean a shared shop.
Question 3. Which finding, if true, would most support the interpretation that one workshop printed both books?
Explanation: Choice D is the best answer because the skeptic grants that workshops copied one another's styles, so a shared look is not enough; the evidence must point to the very same physical type. Identical nicks and worn edges on particular letters are the fingerprints of one set of type, which a rival workshop imitating the style could not reproduce. Choice A is wrong because the two books sharing a decade places them in the same era but does not tie them to one workshop. Choice B is wrong because the same number of lines per page is a layout choice another workshop could copy, so it does not establish a shared shop. Choice C is wrong because a fashionable decorative initial is exactly the kind of shared style the skeptic says imitation can explain, so it does not settle the question.
Surveyors measured the share of coral that was bleached in three zones of a reef before and after a marine heatwave: a shallow flat, a channel, and a deep slope. They concluded that the heatwave struck mainly the most exposed zone, reasoning that the shallow flat, where warm water lingers, should show a sharp rise in bleaching while the deeper, better-flushed zones change little.
Question 4. Which choice best describes data from the graph that support the surveyors' conclusion?
Explanation: Choice C is the best answer because the conclusion is that the heatwave hit mainly the most exposed zone, which is a claim that bleaching rose on the shallow flat but not elsewhere. The graph shows the shallow flat leaping from about eighteen to fifty-four percent while the channel and deep slope hold nearly steady, exactly the concentrated effect described. Choice A is wrong because the shallow flat having the highest cover after the heatwave is a single after reading and does not show that its bleaching rose while the others held steady. Choice B is wrong because the zones starting close together before the heatwave sets the baseline but says nothing about which zone changed afterward. Choice D is wrong because the deep slope holding near fifteen percent describes one unchanged zone alone and does not capture the jump on the shallow flat that the claim rests on.
One coastal bay sees tides far higher than the open coast just outside it. An oceanographer proposed that the bay's shape sets up a natural resonance, so that the tide sloshing in and out matches the basin's own rhythm and builds to great height. A colleague suggested instead that the incoming ocean tide is simply unusually strong where this bay happens to sit.
Question 5. Which finding, if true, would most help distinguish between the two explanations?
Explanation: Choice B is the best answer because the two explanations differ on whether the bay's shape or the incoming tide produces the great height, so the deciding evidence holds the ocean tide constant and varies the shape. A neighboring bay open to the same tide but shaped not to resonate showing only ordinary tides points to resonance, since the same incoming tide does not pile up without the matching shape. Choice A is wrong because the bay's tides being famously high for centuries restates the puzzle rather than testing which explanation accounts for it. Choice C is wrong because the bay drawing visitors speaks to its appeal, not to whether resonance or a strong ocean tide causes the height. Choice D is wrong because the tides following the usual spring and neap cycle is true of tides everywhere and does not separate the basin's shape from the incoming tide.