Question 1
Scientists agree that our planet is getting warmer. But is there a human cause for global warming, or is it a natural fluctuation in a long-term cycle? Warming cycles throughout Earth's history have caused glacial melting, animal and plant habitat shifts, and earlier flowering seasons for trees. These climate changes often correlate with changes in Earth's orbit known as Milankovitch cycles. For example, Earth's angle of axial tilt varies over the course of 41,000 years from 22.1° to 24.5%. At greater angles, Earth's poles receive more direct solar radiation, or insolation.
Increased insolation results in higher mean temperatures. The Milankovitch theory proposes that cycles in climate arise from these cyclical changes in Earth's orbit. According to one viewpoint, the current warming of our planet is just evidence of a Milankovitch cycle. However, current climate changes are occurring at a faster rate than those in the To explain the different rates, many scientists point to human use of fossil fuels. Fossil fuels release carbon dioxide (CO,) when burned. CO, traps thermal radiation in Earth's atmosphere, a phenomenon known as the greenhouse effect. Recent increased levels of CO, correlate very strongly with increased mean temperatures. Furthermore, the rate of Increase in CO, levels is also rising.
For this reason, many scientists conclude that climate change is anthropogenic (caused by humans). Data that support Milankovitch cycles do not necessarily contradict this conclusion. Supporters of the anthropogenic climate change model only need to demonstrate that the current warming deviates from Milankovitch cycles and that human activities provide a better explanation, Both the anthropogenic climate change model and the Milankovitch theory are consistent with some of the observed climate changes. However, only one offers the best explanation for the current warming of Earth.
Where in the passage should the following sentence be inserted? 'Scientists have different explanations for these results:'
Rationale
Immediately before sentence 8 is the best placement for the sentence 'Scientists have different explanations for these results.'
This positioning introduces the contrasting viewpoints of scientists effectively just before the discussion of specific results, allowing for a smoother transition into varying interpretations and enhancing the overall coherence of the passage.
A) Immediately before sentence 1
Placing the sentence before sentence 1 would disrupt the introduction of the topic and misplace the context. The passage likely begins with a general statement or background information that sets the stage for the results, making this location ineffective for introducing differing explanations.
B) Immediately before sentence 4
Inserting the sentence before sentence 4 may not be optimal because it potentially interrupts the flow of ideas already being presented. If sentence 4 discusses specific results, introducing differing explanations too early could confuse readers before they understand the results being referenced.
C) Immediately before sentence 8
This choice is the most logical placement because it allows the sentence to segue into the detailed analysis of the results presented in the preceding sentences. By placing it here, the contrasting explanations can be appropriately contextualized, as readers will already be familiar with the results being discussed.
D) Immediately before sentence 11
Choosing this option would position the sentence too late in the passage. By the time readers reach sentence 11, they may have already formed conclusions based on earlier explanations. This late insertion may diminish the impact of the differing explanations because the context would have already been established without them.
Conclusion
The most effective placement for the sentence 'Scientists have different explanations for these results' is immediately before sentence 8. This location ensures that readers have adequate background on the results before encountering the contrasting interpretations, thus enhancing the clarity and flow of the overall argument presented in the passage. Proper placement of such sentences is crucial for maintaining coherence and ensuring that the reader can follow the author's reasoning logically.