Question 161·200 Super-Hard SAT Reading Questions·Information and Ideas
Mean biomass gained during the second treatment period (grams)
| Initial treatment | Second treatment | Line R | Line S |
|---|---|---|---|
| Well-watered | Well-watered | 5.0 | 4.4 |
| Mild drought | Well-watered | 4.5 | 4.0 |
| Well-watered | Severe drought | 2.0 | 1.7 |
| Mild drought | Severe drought | 2.8 | 2.3 |
Researchers studying drought memory—the possibility that exposure to drought can influence a plant's response to later conditions—conducted an experiment using two genetically distinct lines of grass. The plants were randomly assigned to an initial ten-day period of either mild drought or regular watering. All plants were then rewatered until their leaf water status no longer differed by initial treatment. Finally, the plants underwent a fourteen-day period of either severe drought or regular watering. To distinguish lasting effects of the initial treatment from incomplete recovery, the researchers measured only the biomass gained during the final period. Based on the results, the researchers concluded that _____
Which choice most effectively uses data from the table to complete the statement?
For a command-of-evidence question involving an experiment, identify the controlled comparisons required by the claim. Here, hold the grass line and second treatment constant while changing only the initial treatment. Repeat that comparison across both later conditions and both lines, then choose the answer that accurately describes the complete pattern rather than only one part of it.
Hints
Hold other factors constant
Within each grass line, compare rows that have the same second treatment but different initial treatments.
Check both later conditions
Determine the effect of the initial mild drought separately for plants that later experienced severe drought and plants that later received regular watering.
Look for consistency and reversal
Ask whether the initial treatment has the same effect under both later conditions and whether the pattern occurs in both lines.
Step-by-step Explanation
Make controlled comparisons
To identify the effect of the initial treatment, compare plants from the same line that received the same second treatment but different initial treatments.
Examine the severe-drought results
During later severe drought, previously droughted plants gained more biomass than previously well-watered plants: 2.8 versus 2.0 grams in line R and 2.3 versus 1.7 grams in line S.
Examine the well-watered results
During later regular watering, previously droughted plants gained less biomass: 4.5 versus 5.0 grams in line R and 4.0 versus 4.4 grams in line S. Because the effect reverses depending on the second treatment, the data support a context-dependent drought memory in both lines.