A table question about a study tests whether the numbers support the researchers’ explanation. Read the conclusion and separate the possible causes, then read the table’s title and columns. Match each treatment to the cause it tests and compare it with its untreated group. A control shows what the treatment does when the suspected cause is absent. Accurate numbers aren’t enough if they show a treatment’s effect without testing the full explanation.
Hints
- Hint 1
Go back to the conclusion and separate the two possible causes. Which treatment was designed to test each one?
- Hint 2
Use untreated P-conditioned medium as the starting point. Subtract its growth value from each treated value to see how much each treatment changed growth.
- Hint 3
What does the fresh-medium control tell you about activated carbon’s effect when strain P hasn’t grown in the medium?
Step-by-step
Compare the treatments and their control
Step 1Match each cause to a treatment
The conclusion contrasts releasing an inhibitory compound with consuming nutrients, so we need to test both possible causes. How do the treatments do that? Nutrient restoration replaces what strain P might have used, while carbon treatment removes compounds left behind. The treatments let us compare the two explanations.
- Step 2
Measure the recovery after nutrient restoration
The table’s title names strain R, and its number column shows growth as increases in optical density. Did the treatment that restored glucose and nitrogen restore strain R’s growth? Growth rose from 0.29 to 0.33, a gain of 0.04, still far below fresh medium’s 0.96. Replacing nutrients brought little recovery, so nutrient loss doesn’t explain most of the drop in growth.
- Step 3
Use the control to explain carbon’s effect
What happens with activated carbon, which traps many extracellular organic compounds? Growth in conditioned medium rose from 0.29 to 0.88, a gain of 0.59. Could carbon itself have fed that growth? It cannot be consumed by strain R, and growth in the fresh-medium control changed from 0.96 to 0.92, only 0.04 lower. The large recovery is tied to the conditioned medium, which supports removing a harmful compound rather than supplying food.
- Step 4
Choose evidence that covers the full explanation
Which choice uses both tests and the control to explain why strain P suppresses strain R primarily by releasing an inhibitory compound? The choice describing little recovery after nutrient restoration, substantial recovery after carbon treatment, and only a small effect in fresh medium links every needed comparison to the main cause. Choice A.