Question: A research study concluded that people who work longer hours increase their chances of having higher blood pressure. This conclusion was developed from a study of 200 men of different ages. How is this investigation biased?

  Options: 
 A. The sample size was too large.
 B. Scientists did not run the study.
 C. Women were excluded from the study.
 D. No medication was given to the men. 
Answer: C