Drill 21 · Reading & Writing · Hard Command of Evidence
SAT R&W Command of Evidence (Hard) — Drill 21 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.
This set turns on what a fossil bed can and cannot tell you. Each item hands you a finding about how bones came to rest where they did, then asks which single piece of evidence settles a dispute about the cause. The data items pair a table and a line graph; read both for what they measure rather than for the largest number on display. The quotation item draws from a nineteenth-century story.
At a riverbank quarry, a paleontologist uncovers hundreds of bones from a single species of grazing mammal packed into one thin layer. Perhaps the animals died together at this spot -- maybe at a dried-up watering hole -- and were buried where they fell. Or perhaps the bones accumulated somewhere else and a flood swept them downstream, dropping them here as the current slowed, so the layer is a transported jumble rather than a death site. The two possibilities leave different physical signatures in how the bones lie, and the paleontologist maps the orientation and condition of every bone before any is removed.
Question 1. Which finding, if true, would most strongly support the transported-accumulation account over the buried-in-place account?
Explanation: Correct: Moving water lines up elongated bones with the flow, so a shared long-axis orientation matching the current is the signature transport leaves and in-place burial does not. That orientation is what tells the two accounts apart. A: A full range of ages fits a herd that died together, which leans the other way; at best it is neutral to transport, not support for it. C: Finding the species elsewhere shows it lived in the region but says nothing about whether these particular bones were moved. D: Scavenger marks show the carcasses were exposed before burial, which can happen at a death site too; they do not indicate transport.
Table: bones recovered at three points along the buried channel
To probe whether a flood sorted the bones as it carried them, the team samples three sites strung along the fossil channel and records, for each, the average skeletal completeness for each identified individual (the share of an animal's bones still present) and the average length of the individual bone fragments. The upstream and midstream values are shown; the downstream row is left for you to complete. If a current sorted the material, the lighter, more easily carried pieces should travel farthest, so the trend already visible from upstream to midstream should continue to the downstream site.
Question 2. Which values, entered for the downstream site, would best continue the pattern expected if a current sorted the bones by carrying lighter pieces farthest?
Explanation: Correct: From upstream (82%, 14 mm) to midstream (64%, 9 mm) both completeness and fragment length fall, the signature of a current carrying light, small pieces farthest. Continuing that trend, the downstream site should be lower on both: 39% and 4 mm is the only option that does so. A: 78% and 16 mm rise above the upstream values, reversing the downward trend instead of continuing it. B: 71% completeness sits between the upstream and midstream values rather than below them, and 11 mm is larger than midstream -- the trend does not continue. D: Completeness falls to 44%, but 12 mm fragments are larger than midstream's 9 mm, so the fragment-size trend reverses; only one of the two measures continues.
In a student's literature essay, the writer argues that the narrator of Charlotte Perkins Gilman's 1892 story first presents the rented estate as appealing precisely because it stands so far from other people, an isolation the essay later reads as ominous. The student wants a line in which the narrator dwells on how remote and set apart the house is.
Question 3. Which quotation from the story most effectively illustrates the student's claim about the house's isolation?
Explanation: Correct: The claim is about isolation, and this line names the distances directly -- set back from the road, three miles from the village -- making the house's remoteness the point. It matches the student's argument exactly. B: The garden line praises the grounds' beauty, not the estate's distance from other people. C: This describes the narrator writing in the nursery; it touches privacy, not the house's physical isolation. D: This describes the wallpaper's color, unrelated to where the house stands.
Returning to the main bone layer, a second researcher proposes that the whole bed was carried in by one violent flood, citing the bones' shared alignment. A colleague is skeptical. She agrees a current can align loose bones, but argues that the deposit was not transported far, if at all, and that the alignment formed in place as shallow water washed back and forth over carcasses that were already lying here. To decide between a long flood transport and near-in-place reworking, she looks for evidence about whether the skeletons were still held together when the water reached them.
Question 4. Which finding, if true, would most weaken the claim that the bones were carried in from far away by a single flood?
Explanation: Correct: Small foot and ankle bones fall apart and scatter once soft tissue rots, so finding them still joined means the carcasses were buried before much decay and could not have tumbled far down a river. That undercuts long-distance flood transport. A: Shared alignment is the very evidence the transport claim rests on; it supports that claim rather than weakening it. B: Water-laid sand is consistent with a flood, so it tends to fit the transport claim, not undercut it. C: A mix of individuals is expected whether the bones were swept together or died together, so it does not tell against transport.
Exposed bone cracks and flakes the longer it sits at the surface, but once sediment buries it the weathering essentially stops. The team uses a standard weathering score (0 for fresh, 5 for badly degraded) and suspects two parts of the bed were buried at different speeds: one patch was smothered by sediment within a few months of death, the other lay exposed far longer before burial. They score bones from each patch and plot the average weathering score against months since death. Because all the bone starts fresh, the two lines begin together at zero; what differs is what happens once burial does or does not intervene. The graph shows the two lines over the first year after death.
Question 5. Which statement is best supported by the graph?
Explanation: Correct: Burial halts weathering, so the rapid-burial line rises briefly and then flattens once sediment covers the bone, while the slow-burial line keeps climbing as long as it stays exposed. That trend-break -- one line plateauing, the other rising on -- is what the graph establishes. A: By year's end the slow-burial patch scores higher, not the rapid-burial one, so this reverses the final ranking on the graph. C: Neither line reaches the top of the scale within the year plotted; both stay below the maximum. D: The lines separate after the shared start -- one plateaus, one keeps rising -- so they do not share a score at every later point.