1 and 2 standard deviations below the mean are the scores 21 - 1 × 6 = 15 and 21 - 2 × 6 = 9, and a score between 15 and 9 is only [spoiler]12 in the choices.
D[/spoiler]
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
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