The Core Argument:
- Premise 1: Laws requiring bicycle helmets are intended to reduce injuries.
- Premise 2: Some bicycle safety advocates argue these laws should be repealed because they can, in some circumstances, have the contrary effect (i.e., increase injuries or fail to reduce them effectively).
- Goal: Find an option that explains why mandating helmets might lead to a contrary effect (more injuries or less safety).

Analyzing the Options:
- A. Classes that teach safe bicycling behaviors have been shown to be a more effective method of reducing injuries than are laws requiring helmets.
- This suggests an alternative or better method for reducing injuries. However, it doesn't explain how helmet laws themselves could have a contrary effect (i.e., cause more injuries or actively undermine safety). It just says another method is superior.
- B. A driver overtaking a cyclist who is not wearing a helmet is more likely to pass at a safe distance than if the cyclist were wearing a helmet.
- This is a strong candidate. If drivers pass closer to helmeted cyclists, it increases the risk of collision for those cyclists. This directly supports the idea that wearing a helmet (due to the law) could lead to a contrary effect on safety by altering driver behavior in a negative way, even if the helmet itself offers protection in a crash. It explains how the law's existence (leading to more helmet-wearing) could paradoxically make cycling more dangerous in some circumstances.
- C. Bicycle helmet laws have been shown to discourage people from bicycling.
- If fewer people bicycle, there might be fewer total bicycle injuries. However, this doesn't explain how the law has a contrary effect on safety for those who do ride. It explains a societal impact, not a safety paradox. Moreover, fewer cyclists might mean fewer injuries, not more, so it doesn't support the "contrary effect" related to injury incidence.

- D. Children are more vulnerable to head injuries while bicycling than are adults.
- This explains why laws might primarily apply to children, but it doesn't explain how helmet laws for anyone (children or adults) could have a contrary effect on injury reduction. It's a statement about vulnerability, not a paradoxical outcome of the law.
- E. In some severe bicycle crashes, a helmet may not prevent traumatic brain injury.
- This highlights a limitation of helmets (they're not foolproof), but it doesn't explain how the law or the wearing of a helmet could have a contrary effect leading to more injuries overall. It just states that a helmet isn't a guarantee against all injury.

Conclusion:

Option B directly explains how a helmet law, by influencing driver behavior, could inadvertently increase the risk of accidents, thereby having a "contrary effect" on safety for cyclists who comply with the law. This creates the paradox the advocates describe.

The final answer is B .