A table question about a scientific claim tests whether you can connect the numbers to what the claim says caused a change. Read the claim, then find what the passage says each possible cause would do to the measurements. Check the table's title, columns, and starting values, so you can compare changes, not only final values. Check both measurements together, because a number can be accurate without showing which cause did most of the work.
Hints
- Hint 1
Look in the first paragraph for the effects each process has on the enrichment index.
- Hint 2
Work out both changes in each flooded group using the initial nitrate concentration of 12.0 milligrams per liter and enrichment index of 4.0.
- Hint 3
What does the flooded group without plants let you test about the source of nitrate loss?
Step-by-step
Connect the measured changes to their cause
Step 1Tell the two processes apart
The passage says denitrification lowers nitrate concentration while raising the enrichment index, but root uptake lowers nitrate with little change in the enrichment index. What separates these causes of nitrate loss in flooded soil? The index change helps identify the process, since a nitrate drop alone fits either cause.
- Step 2
Calculate the flooded groups' changes
The table reports final values after 14 days, so compare its columns with the starting values: 12.0 milligrams per liter and an enrichment index of 4.0. How much did the flooded groups change? Without plants, nitrate fell by 12.0 − 6.8 = 5.2 milligrams per liter, and the index rose by 8.7 − 4.0 = 4.7 points. With plants, the loss was 5.4 milligrams per liter and the rise was 4.9 points, so both groups lost nitrate while their indexes rose sharply.
- Step 3
Test whether roots were needed
Could roots explain the loss in flooded soil without plants? Root uptake can't occur without plants, yet the no-plant group lost almost as much nitrate as the planted group. Nearly all removal was expected through either plant-root uptake or denitrification, so the large loss without roots points to denitrification. The sharp index increases in both flooded groups also support it as the main cause.
- Step 4
Match the full finding
The finding with more than 5 milligrams per liter of nitrate loss and an index rise of at least 4.7 points matches both flooded groups' changes. The words regardless of whether plants were present support denitrification rather than plant-root uptake, because the large loss didn't depend on roots. Choice A.