SAT OwlQuestion bank / Command of Evidence
| Lake | Phosphorus (micrograms per liter) | Algae, as chlorophyll (micrograms per liter) | Average water temperature (C) |
|---|---|---|---|
| Arlo | 12 | 4 | 18 |
| Birch | 35 | 21 | 19 |
| Crane | 38 | 9 | 11 |
| Dell | 60 | 33 | 20 |
A researcher studied four lakes and concluded that higher phosphorus levels tend to be associated with more algae, but that cold water may limit algae growth even when phosphorus is plentiful.
Which choice most effectively uses data from the table to support the second part of the researcher's conclusion?
Dell had the highest phosphorus level and the most algae of the four lakes.
Crane had a phosphorus level similar to Birch's but far less algae, and its water was much colder than Birch's.
Arlo had the lowest phosphorus level and the least algae of the four lakes.
Birch and Dell had average water temperatures within one degree of each other.
Show answer and explanation
Answer: B
The second part of the conclusion says cold water can hold algae down even when phosphorus is high. Crane and Birch have similar phosphorus (38 and 35), yet Crane has much less algae (9 vs. 21) and much colder water (11 vs. 19 degrees). Choice B makes exactly that comparison.
Choices A and C are accurate, but they support the first part of the conclusion, the general link between phosphorus and algae, not the effect of cold water.
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