Question 141·Hard·Command of Evidence
Refer to the following graph.
Quartz Crystal Growth Rate in Hydrothermal Fluid at Different Temperatures
![graph]
In a laboratory simulation of hydrothermal mineral formation, researchers grew quartz crystals in a hot, water-based fluid. Although higher temperatures can speed up chemical reactions, the results suggest that once temperatures are already high, another factor may limit how much faster the crystals can grow, as evidenced by the fact that ____
Which choice most effectively uses data from the graph to complete the text?
For command-of-evidence questions tied to a graph, first restate the claim the blank must support (here: growth rate levels off at high temperatures). Then identify the specific part of the graph that corresponds to that claim (the highest temperature points) and choose the option that most directly and accurately reports that high-end comparison, avoiding choices that use the wrong interval or misstate the magnitude of the change.
Hints
Focus on the phrase “already high”
That wording points you to the highest temperatures on the graph, not the lower ones.
Compare the two highest points directly
Read the values at 300°C and 350°C and note how small the change is.
Be wary of near-miss number claims
If an option gives a numerical difference between 300°C and 350°C, check whether that difference matches the graph’s values.
Step-by-step Explanation
Identify what the blank must support
The blank needs to provide graph-based evidence that at already high temperatures, increasing temperature further yields only a small additional increase in quartz crystal growth rate.
Use the highest-temperature data points
From the graph, the average growth rate is about 2.1 mm/day at 300°C and about 2.2 mm/day at 350°C. That change is very small (about 0.1 mm/day), indicating the growth rate is leveling off at the high end.
Choose the option that states that relationship accurately
The best completion is the one that accurately describes the very small difference between the two highest temperatures.
Therefore, the correct choice is: the average growth rate at 350°C is only slightly greater than the average growth rate at 300°C.