This problem tests estimation and interpretation of scatter plots. The first 10 measurements (before the red line) cluster around an average of approximately 140 mmHg. The second set of 10 measurements (after the red line) cluster around approximately 170 mmHg. To estimate the increase, subtract the earlier average from the later average: 170 − 140 = 30 points. Therefore, option C is correct. Options A and D represent total values rather than the change between averages. Option B overestimates the difference. On the NEX, estimation questions do not require exact calculations; instead, you must identify reasonable average values from visual data and compare them correctly.

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