Question 191·200 Super-Hard SAT Reading Questions·Expression of Ideas
Marine biologists once believed deep-sea hydrothermal vents were isolated pockets of life, teeming with unique species that evolved in complete genetic isolation from surface ecosystems. ______ recent genetic analyses have revealed extensive gene flow between vent organisms and their shallow-water relatives, undermining the notion that vent communities are evolutionary islands.
Which choice completes the text with the most logical transition?
For transition questions, first ignore the answer choices and read the sentence or sentences around the blank to decide the logical relationship (addition, contrast, cause-effect, example, etc.). Put in your own simple word like "but," "so," or "for instance" to test the relationship, then look at the choices and pick the one whose function matches that relationship. Always check that the transition makes sense in both meaning and direction (supporting vs. contradicting) before you move on.
Hints
Look at how the second idea treats the first
Ignore the blank and read from the beginning to "evolutionary islands." Ask: does the second part agree with the original belief about hydrothermal vents, or does it weaken or challenge that belief?
Focus on the phrase "undermining the notion"
The words "undermining the notion" tell you how the new information relates to the earlier idea. Think about whether that phrase suggests support, addition, result, or opposition.
Match the general meaning of each transition type
Think of the roles of the four transitions: one introduces an example, one adds another similar point, one shows a result, and one shows contrast. Which role fits a sentence where new evidence goes against an old belief?
Test each option in the sentence
Read the sentence with each choice in the blank and ask: Does this word correctly show the logical connection between an old belief and new evidence that weakens that belief?
Step-by-step Explanation
Understand the relationship between the two ideas
Read the sentence around the blank without any transition:
"Marine biologists once believed deep-sea hydrothermal vents were isolated pockets of life, teeming with unique species that evolved in complete genetic isolation from surface ecosystems. Recent genetic analyses have revealed extensive gene flow between vent organisms and their shallow-water relatives, undermining the notion that vent communities are evolutionary islands."
The first sentence states an old belief (vents are isolated and genetically separate). The next clause explains that new genetic analyses undermine that belief. So the relationship between the two is contrast: new evidence is going against the old idea.
Decide what kind of transition is needed
Because the new information challenges or contradicts the earlier belief, you need a transition that shows contrast, not one that gives an example, adds similar information, or shows a cause-and-effect result.
Ask yourself: “Is the writer supporting and continuing the first idea, or overturning it?” Here, the phrase "undermining the notion" clearly shows that the second part goes against the first idea. That means the correct transition must signal a shift or opposition.
Match each option to its relationship type
Now look at what each choice usually does in a sentence:
- "For example," introduces a specific example of the previous idea.
- "Furthermore," adds more information in support of the same idea.
- "Consequently," introduces a result or effect of what came before.
- One option shows contrast, signaling that what follows goes against or in spite of the previous statement.
Since we already know the second clause disagrees with the earlier belief, only the contrast transition fits the sentence’s logic.
Select the transition that shows contrast
The only option that signals this needed contrast is "Nevertheless,", which means something like “in spite of what was just said.” It correctly links the old belief to the new, conflicting evidence:
"Marine biologists once believed... Nevertheless, recent genetic analyses have revealed..."
So the correct answer is D) Nevertheless,.