For every 50 dogs that contract a certain disease, one will die from it. A vaccine exists that is virtually 100 percent effective in preventing this disease. Since the risk of death from complications of vaccination is one death per 5, 000 vaccinations, it is ttherefore safer for a dog to receive the vaccine than not to receive it. Which one of the following would it be most helpful to know in order to evaluate the argument? ['the number of dogs that die each year from diseases other than the disease in question', 'the total number of dogs that die each year from all causes taken together', 'whether the vaccine is effective against the disease in household pets other than dogs', 'the likelihood that an unvaccinated dog will contract the disease in question']