Here's a problem to solve: 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?

Among the 4 following options, which is the correct answer?

- 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.
 