Casey: it should be a law that skiers must wear helmets, just like passengers in a car must wear seat belts

alex: but then where do you draw the line? would it be fair to say that all hikers must wear kneepads?

casey: no, but for things that are more dangerous, like driving and skiing, there have to be safety laws.

alex: saying something is "more dangerous" is very subjective. who gets to decide?

which statement would be the strongest cause of bias in the discussion?
a. alex does not participate in sports or outdoor activities.
b. alex has never been skiing.
c. casey's brother was hurt in a skiing accident.
d. casey's dad is a politician.