Question

Read the passage carefully and answer the following question.
Geologists have been investigating a potential cycle in geological events for a long time. Back in the 1920s and 30s, scientists of the era had suggested that the geological record had a 30-million-year cycle, while in the 1980s and 90s researchers used the best-dated geological events at the time to give them a range of the length between 'pulses' of 26.2 to 30.6 million years. Now, everything seems to be in order – 27.5 million years is right about where we'd expect. A study late last year suggested that this 27.5-million-year mark is when mass extinctions happen, too.
Which of the following statements can be BEST concluded from the passage?

• A. Geological disasters happen sporadically
• B. Not all species go extinct once every 27.5 million years
• C. Mass extinctions and “geological pulse” are correlated
• D. “Pulse” between geological events is constant
• E. All species go extinct once every 27.5 million years

Answer 1

The Correct Option is C

The passage discusses a recurring cycle in geological events, suggesting that major geological "pulses" happen approximately every 27.5 million years. It also mentions a study indicating this period aligns with occurrences of mass extinctions. Therefore, the question asks us to determine the best conclusion that can be drawn from the passage.

Analyze the Options:

• Option 1: "Geological disasters happen sporadically" implies randomness, which is the opposite of the cyclical pattern described in the passage, so this cannot be concluded.
• Option 2: "Not all species go extinct once every 27.5 million years" might be true generally, but it does not address the main point of the passage—correlation between geological pulses and mass extinctions.
• Option 3: "Mass extinctions and 'geological pulse' are correlated" directly aligns with the passage, which discusses a study finding a link between these occurrences.
• Option 4: "'Pulse' between geological events is constant" implies a fixed interval without deviation, while the passage only suggests an average recurring cycle rather than a strict interval. Thus, it is not fully accurate.
• Option 5: "All species go extinct once every 27.5 million years" overstates the passage, which talks about mass extinctions affecting many species but not necessarily all.

Conclusion and Final Answer:

The best conclusion from the passage is option 3, "Mass extinctions and 'geological pulse' are correlated," because the passage provides details about research suggesting that these events align, supporting this correlation.

Answer 2

The passage highlights how researchers discovered a cycle of about 27.5 million years in geological events. Recent studies suggest that mass extinctions also occur at this same interval. This indicates a correlation between geological cycles (pulses) and mass extinctions.

Why Option 3 is BEST 

• The passage directly states that mass extinctions align with the 27.5-million-year pulse.
• This is a clear sign of correlation, which is the most accurate conclusion.

Why Other Options Are Incorrect

• Option 1: Wrong — The passage stresses a patterned cycle, not sporadic events.
• Option 2: True in reality, but not directly supported by the passage. The focus is on the cycle itself, not exceptions.
• Option 4: Incorrect — The pulse is not constant; earlier ranges varied (26.2–30.6 million years). Only recently was 27.5 million years estimated.
• Option 5: Wrong — The passage does not claim that all species go extinct every 27.5 million years.

Key Takeaway

The passage emphasizes the connection between geological cycles and mass extinctions. Thus, the best conclusion is Option 3: Mass extinctions and “geological pulse” are correlated.