This question is difficult because once you spot the flaw, it is hard to put it into words, which is why I missed it. I couldn't figure out how any of the answer choices paraphrased the flaw, so I had to pick an answer and move on. I don't really see how C is the flaw and how A is worse than C.
Bike riders don't follow the rules of the road, and this is a causal factor in 25% of traffic accidents involving bikes. The lack of bike saftey equipment is also a causal factor in 25% of those accidents. Thus, bikes are partly responsible for more than half of the traffic accidents involving bikes.
What I am looking for: I think the flaw is a math error. The conclusion says that 50+%, but we are given information about a causal factor being 25% and of those accidents a causal factor is 25%. Instead of additive, the relationship should be multiplicative. The conclusion should only talk about the percentage of bike accidents that included inadequate bike saftey equipment.
Answer A: This was the answer I chose, and I don't see how this doesn't adequately point out the flaw. Sure, you need to make an assumption that motorists are a factor in traffic accidents, but how is that not a reasonable assumption that the author overlooked? Additionally, since we conclude that 50+%, this is implying that less than 50% ("less than half") have some other cause. But, since we can't conclude anything about 50+%, this presumption is not justified. I don't see what is wrong with this one.
Answer B: No. We are to take the causal premises as truth.
Answer C: How is this the correct answer choice? Doesn't the conclusion say "at least partially responsible?" Thus, the argument DOES consider the possibility that more than one factor may contribute to a given accident? Additionally, the argument isn't talking about "all/given accidents;" it is limited to accidents involving bikes. How can the flaw be about "given" accidents?
Answer
We don't need a source.
Answer E: Who cares about the severity of injury?