SAT OwlQuestion bank / Command of Evidence
| Mulch type | Soil moisture (%) | Weeds per square meter |
|---|---|---|
| None (bare soil) | 14 | 38 |
| Straw | 22 | 12 |
| Wood chips | 25 | 9 |
| Gravel | 18 | 35 |
An agricultural researcher compared vegetable beds covered with different mulches with beds of bare soil. She concluded that although gravel helped the soil hold moisture better than bare soil did, it was far less effective than the other mulches at keeping weeds down, offering almost no improvement over bare soil.
Which choice most effectively uses data from the table to support the researcher's conclusion about gravel?
Beds with wood chips had the highest soil moisture, 25 percent, and the fewest weeds, 9 per square meter.
Beds with straw had 12 weeds per square meter, while beds with gravel had 35 weeds per square meter.
Beds with gravel had 18 percent soil moisture, higher than the 14 percent in bare soil, but 35 weeds per square meter, nearly as many as the 38 in bare soil.
Beds with gravel had 18 percent soil moisture, lower than the 22 percent in beds with straw.
Show answer and explanation
Answer: C
The conclusion makes two points about gravel: it beat bare soil on moisture, and it barely beat bare soil on weeds. Choice C gives both comparisons: 18 percent versus 14 percent moisture, and 35 versus 38 weeds per square meter.
Choice B shows gravel trailing straw on weeds, but it leaves out the moisture benefit and the near tie with bare soil.
Why the other choices are wrong
- A. This shows wood chips did well but says nothing about gravel, the subject of the conclusion.
- B. This shows gravel trailing straw on weeds but leaves out the moisture gain and the comparison with bare soil.
- D. This compares gravel's moisture with straw's, but the conclusion compares gravel with bare soil and also concerns weeds.
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