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N (Not Applicable): Activity is not applicable to this occupation.
O (Occasionally): Occupation requires this activity up to 33% of the time (0 - 2.5+ hrs/day).
F (Frequently): Occupation requires this activity from 33% - 66% of the time (2.5 - 5.5+ hrs/day).
C (Constantly): Occupation requires this activity more than 66% of the time (5.5+ hrs/day).
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