Question 138·Hard·Central Ideas and Details
Marine biologists attempting to chart the migratory routes of Atlantic sturgeon through one of the world’s busiest shipping corridors have adopted an unusual strategy. Each fish is fitted with a rice-sized acoustic tag that transmits a signature sequence of sound pulses. Ship engines, sonar, and industrial dredging generate a cacophony that would normally mask conventional tracking signals, but the distinctive digital “chirp” of each tag is recognized by underwater receivers anchored along the corridor. By correlating the time stamps from multiple receivers, the researchers can calculate each fish’s speed and path with meter-level accuracy.
According to the text, why is it important that each acoustic tag transmits a signature sequence of sound pulses?
For “According to the text” questions, go back to the specific sentence or two that mention the key phrase (here, “signature sequence of sound pulses”), then restate that part in your own words before looking at the choices. Eliminate any answer that changes the mechanism the passage gives (recognition of a distinctive signal in noise) or adds a different mechanism (louder signals, direct distance measurement, clock synchronization), and choose the option that most directly paraphrases what the text actually says.
Hints
Zoom in on the bolded phrase
Focus on the sentence with “signature sequence of sound pulses” and read the sentence that follows it. Ask yourself: what problem are the scientists facing?
Identify the challenge in the environment
What does the passage say about ship engines, sonar, and dredging? How do these affect normal tracking signals?
Connect the unique signal to its role
The passage contrasts “conventional tracking signals” with the “distinctive digital ‘chirp’” of each tag. How does this contrast help you see what the unique sound sequence is used for?
Step-by-step Explanation
Locate the key sentence in the passage
Find where the passage talks about the signature sequence of sound pulses. The key information comes in the sentence beginning with “Ship engines, sonar, and industrial dredging generate a cacophony…” and continuing through how the receivers work.
Understand the problem and the solution described
The passage says ship engines and other human activities make a cacophony (very loud, mixed noise) that would normally mask conventional tracking signals. Then it contrasts that with the distinctive digital “chirp” of each tag, which is recognized by underwater receivers anchored along the corridor. So the unique sound pattern of each tag is the solution to the noise problem.
Restate the relevant idea in your own words
Put that information into your own words: the area is very noisy, so normal tracking signals would be hidden. Because each tag has a unique pattern that receivers can recognize, the system can still detect and tell apart signals from different fish in all that noise.
Match that idea to the answer choice
Now look for the option that says the unique sound sequence lets the receivers distinguish one fish’s signal from others and from the background noise. Choice A is the one that matches this idea, so A) It allows receivers to identify individual fish even amid heavy background noise is the correct answer.