A central idea question tests whether you can name the point of the whole text. Name the topic, then find the turn where the writer moves away from an earlier view. When studies describe both sides of a relationship, ask what the results show together. Predict the main idea in one sentence that explains the results and the change in view. A true detail can still be too narrow to cover the whole text.
Hints
- Hint 1
Look at the opening sentence and the sentence beginning with Yet. What change in view does that link signal?
- Hint 2
Compare what fungi do with what trees do. What does each side get from the other?
- Hint 3
Use Kiers’s final sentence to interpret the results. What larger point does he draw from the behavior of both fungi and trees?
Step-by-step
Find the point after the turn
Step 1Name the topic and old view
The opening calls mycorrhizal networks selfless conduits that help trees share water and nutrients. What view is it setting up? It presents the networks as a way for trees to help their neighbors without seeking a reward. For a central idea, we need the text’s point about that view, not the opening picture alone.
- Step 2
Read both results after the turn
Where does the opening view change? Yet recent ecological studies reveal a more calculating system marks the turn, where the text moves away from that view. Fungi transport resources only when they receive carbon compounds from trees in return, while trees favor partners that deliver the greatest nutritional payoff. Each side changes what it gives based on what it gets, so both results show a relationship shaped by rewards, not separate facts about fungi and trees.
- Step 3
Predict the main idea
Kiers ties the results to continuous negotiation of costs and benefits. What does that tell us about cooperation? It depends less on generosity than on what each side gains. We can now predict the main idea: the old picture of selfless help misses how fungi and trees cooperate while seeking something in return.
- Step 4
Check what the choice covers
Which choice states the central idea of the text without covering only one partner? Mutually beneficial trade governed by self-interest names the whole relationship. The contrast between Once considered altruistic and now understood also shows the passage’s change in view, so the choice covers both the finding and the view it challenges. Choice C.