A graph question comparing two changes tests whether you can show which change does more for each group. Read the conclusion and identify the starting treatment and both changes, including what any change in intensity means. Then use the title, axes, and key to find the right bars and units. Subtract the starting value from each new value, and check every number a choice gives. True numbers still need to support the whole comparison.
Hints
- Hint 1
Look at the final sentence of the passage. Identify the current lighting and the two proposed changes.
- Hint 2
What graph treatment does halving high-intensity blue light produce? Check how high and low intensity are related in the passage.
- Hint 3
For each species, subtract the settlement rate under the current lighting from the rate under each proposed change. Compare the two results within each species.
Step-by-step
Compare both changes from high blue
Step 1Translate the two changes
The conclusion compares switching to high-intensity amber light with keeping blue light and reducing its intensity by half. Which treatment does halving high blue give us? High-intensity treatments used twice the light level of the low-intensity treatments, so halving high blue gives low blue. We’ll compare high amber with low blue for both species from the same high-blue starting point.
- Step 2
Read the matching bars
The title and vertical axis show settlement percentages, and the key labels the two coral species. Mustard hill coral is the left bar, and mountainous star coral is the right bar. In the order high blue, high amber, then low blue, mustard hill reads 31%, 68%, and 49%; mountainous star reads 24%, 59%, and 41%.
- Step 3
Compare gains from high blue
How much does each change raise settlement? We measure the difference between two percentages in percentage points. For mustard hill, high amber gains 68 − 31 = 37 points, while low blue gains 49 − 31 = 18. Mountainous star gains 59 − 24 = 35 points under high amber and 41 − 24 = 17 under low blue. So high amber gives the larger gain for both species, matching the claim that it would preserve settlement more effectively.
- Step 4
Check the complete comparison
Which choice reports both changes from the site’s high-intensity blue light for both species? The choice beginning Compared with high-intensity blue light gives all four gains correctly: 37 and 35 points for high amber, versus 18 and 17 for low blue. Choice A.