The Following Argument Is Valid or Forceful

The following argument is valid or forceful. Identify the irrelevant premise: Everyone who smokes puts themselves at a higher risk of developing lung cancer. So because Bob smokes 5 packs a day, he has a higher risk than a normal person of developing lung cancer. You have to be an idiot to smoke if this is true.

A) If smoking increases the risk of lung cancer, all people who smoke are idiots.
B) If you smoke, you increase your risk of developing lung cancer.
C) Bob smokes 5 packs of cigarettes a day.
D) Bob has a higher risk of developing lung cancer than a normal person.