Question: We want to conduct a study to assess the effect of exposure to alcohol consumption on pancreatic cancer. It is possible that the relationship may be affected by the effect of exposure to tobacco use. If you only want to analyze the effect of alcohol consumption, what type of bias can occur? 
 Options:  <1> Exposure bias <2> Diagnostic bias <3> Performance bias <4> Bias due to surveillance effect (or Hawthorne). <5> Confusing bias
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