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SAT Reading & Writing: Hard Inferences (Drill 24)

Drill 24 · Reading & Writing · Hard Inferences

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About This Drill

SAT Reading & Writing: Hard Inferences (Drill 24) is a Reading & Writing practice drill covering Hard Inferences. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.

These hard SAT inference questions ask you to complete short academic passages by choosing the conclusion the text best supports. The right answer stays inside the evidence; the wrong ones tend to overreach, reverse the logic, or wander off the passage's point.

Questions & Explanations

Text
The great size of a limestone cave was long put down entirely to a single underground river, whose flow can carve and widen passages over ages. A survey of the cave's walls complicated that account. Many chambers bear the chalky gypsum crusts and corroded, spongelike surfaces left by acid rising from below, where sulfide-rich waters react to make sulfuric acid that eats limestone from within. These acid-worked features appear in galleries the river never reached, and the enlargement traces to both the flowing water and the rising acid at once. The evidence cannot show how much of the cave's volume each carved. Because two agents widened it together, the cave's great size ______

Question 1. Which choice most logically completes the text?

  • A) cannot be attributed to the underground river alone, since acid-corroded galleries the river never reached were widened from within. ✓
  • B) shows the river to have done nothing, because caves of this size are dissolved by rising acid rather than carved by any stream.
  • C) was produced mostly by the rising acid, with the river's carving adding only a minor part of the total volume.
  • D) most likely reflects an ancient collapse of the cavern roof that opened the chambers far wider than water ever could.

Explanation: (A) Acid-corroded galleries appear where the river never flowed, and the cave's volume traces to both the water and the rising acid, so its size cannot be pinned on the river by itself; acid dissolution is an equally real agent the evidence cannot rank against the river. The choice revises the river-only account without denying the river's work. (B) says the river did nothing, contradicting the stated point that flowing water carves and widens passages. (C) ranks the acid above the river, but the evidence cannot separate their shares. (D) invents a roof collapse the passage never raises.

Text
To judge how common a stomach infection was in a region, health officials counted only the cases confirmed at hospitals, where patients arrive when symptoms are severe, and reported that count as the region's caseload. The hospital records were precise and complete for those they covered. But the same infection often produces mild or no symptoms, and people with a light case rarely go to a hospital and so are never tested or counted, however many of them carry it. Because the count could include only those sick enough to seek hospital care, its measure of the infection's spread ______

Question 2. Which choice most logically completes the text?

  • A) proves that nearly everyone who catches the infection develops symptoms severe enough to end up requiring hospital care in time.
  • B) likely understates how common the infection is, since mild and symptom-free cases rarely reach a hospital and so go uncounted. ✓
  • C) is useless for any purpose, because a count taken at hospitals can never be set beside one taken in the wider community.
  • D) probably runs too high, mainly because the region simply has too few hospitals to gather a fair count.

Explanation: (B) The count reaches only patients sick enough to come to a hospital, and mild or symptom-free cases seldom do, so a large share of infections is missing and the tally cannot show how widespread the infection truly is; the choice names that ascertainment gap. (A) treats the hospital cases as the whole, but mild cases were simply not captured. (C) calls the count useless and incomparable, overstating a fixable exclusion. (D) blames the number of hospitals, yet the flaw is who seeks care; more hospitals would still miss those who never seek it.

Text
A conservator analyzing an undated panel painting scrapes a fleck from its bright blue sky and identifies the pigment as a synthetic blue whose recipe, chemists agree, was first prepared in a well-documented year and not before. The blue lies in the painting's original paint layer, beneath the old varnish, not in any later retouching, so the artist used it from the start. Nothing suggests the panel was repainted or the sky added afterward. Because a painter cannot grind a color that chemists had not yet learned to make, the panel painting ______

Question 3. Which choice most logically completes the text?

  • A) must be older than that blue's invention, because so pure and even a sky can only have been laid down before synthetic colors existed.
  • B) can be dated to the very year the blue was first prepared, since the pigment fixes the panel to that single year.
  • C) was most likely painted by an artist who had trained abroad, where the new blue first came into use.
  • D) can be no earlier than the year that blue was first prepared, since its original sky uses a pigment first made only then. ✓

Explanation: (D) The original sky uses a synthetic blue first prepared in a documented year, and it sits in the first paint layer rather than in later retouching, so the artist could not have used it before it existed; the panel therefore cannot be earlier than that year, though it may date from that year or later. The choice states just that earliest-possible bound. (A) makes the panel older than the pigment, but a color made only after its invention cannot appear in an earlier work. (B) claims a precise year, yet the pigment gives an ordering, not a date. (C) guesses at the artist's foreign training, which the passage never mentions.

Text
A regional wine trade's exports jumped in a single year, and the obvious explanation was a bumper grape harvest that left more wine to ship. Estate ledgers, though, record that year's grape yield as ordinary, no larger than the yields of the seasons on either side, so no glut of wine was pressed. What did change that year was the opening of a new deepwater port nearby, through which barrels could reach distant markets far more cheaply than before. Because the harvest that year was unremarkable while the new port had just opened, the new port ______

Question 4. Which choice most logically completes the text?

  • A) most likely mattered far less than a sudden change in foreign tastes that made this region's wine newly fashionable abroad.
  • B) cannot have driven the jump, since that year's grape harvest was plainly far larger than in the surrounding seasons.
  • C) was the only reason any of the region's wine reached foreign markets that year, so that without it no barrels would have shipped.
  • D) does more to explain the jump in exports than an unusually large harvest, since that year's grape yield was no greater than usual. ✓

Explanation: (D) The obvious rival, a bumper harvest, is ruled out directly: the ledgers put that year's yield on a par with the neighboring seasons, so no extra wine was pressed, and the one change that did occur was the new port that cut the cost of reaching distant markets. The port therefore does more to explain the export jump. The choice weighs the port against the specific rival the evidence addresses without making it the sole cause of all trade. (A) credits a shift in foreign tastes the passage never mentions. (B) asserts a large harvest, contradicting the recorded ordinary yield. (C) makes the port the sole reason for any export, but wine shipped in surrounding years too and the evidence speaks to the jump.

Text
In one district, deaths among young children from a common disease fell over a span of years. During those years the district had taken up a new practice of inoculating children against the disease, and an observer asked whether the inoculation lowered the deaths or whether living conditions were simply improving everywhere, easing child mortality on their own. A neighboring district of similar size, wealth, diet, and setting, which had not taken up inoculation, gave a comparison: across the same years its child deaths from the disease held about level. Because deaths fell only in the district that inoculated, the inoculation practice ______

Question 5. Which choice most logically completes the text?

  • A) most likely mattered much less than a cleaner public water supply that the district itself had newly piped in over those same years.
  • B) clearly did nothing, since child deaths from the disease had been falling in both districts alike for years beforehand.
  • C) is a more plausible cause of the fall in child deaths than broadly improving conditions, since only that district saw the fall. ✓
  • D) lowered the deaths chiefly because the inoculating district was already the wealthier and much better-fed of the two districts.

Explanation: (C) Child deaths fell only in the district that inoculated, while a district matched on size, wealth, diet, and setting held level over the same years, so a general easing of conditions everywhere cannot explain a fall confined to one district, and the inoculation better fits the pattern. The choice ties the fall to inoculation without calling it the sole cause. (A) credits a new water supply the passage never mentions. (B) says deaths had been falling in both districts, contradicting the level comparison. (D) blames a wealth-and-diet gap, but the districts were matched on both.