One Must Use Care in Interpreting Occupational Differences in Morbidity

One must use care in interpreting occupational differences in morbidity and mortality because:

A) good health status may be a factor for selection into a job.
B) occupations involving physical activity tend to cause heart attacks among older workers.
C) occupational stress, even in extreme situations, is difficult to quantify.
D) good health status may be a factor for selection into a job, occupations involving physical activity tend to cause heart attacks among older workers, and occupational stress, even in extreme situations, is difficult to quantify.