Final answer:
While the exact multiplier of likelihood is not stated in the provided references, it's clear that helmeted riders are indeed more likely to survive head injuries than those not wearing helmets. Helmets play a crucial role in protecting against these injuries.
Step-by-step explanation:
The question is asking about the likelihood of a helmeted rider surviving a head injury compared to those not wearing helmets. This can often be studied and quantified by using dummies in simulated scenarios. Through such research, it has been found that using a helmet significantly increases the chance of survival against head injuries.
Basing on the provided options, however, the exact multiplier of how much more likely helmeted riders are to survive head injuries is not explicitly stated in the reference information. But keeping in mind the important role of a helmet in protecting against head injuries, it can be interpreted that helmeted riders are certainly more likely to survive head injuries than those not wearing helmets. Comprehensive studies tend to support this.
In conclusion, helmet use is vital for safety while riding to mitigate potential head injuries.
Learn more about Helmet Safety