In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Q: 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
A:
5