A study showed that only 10% of American dog owners enroll their dogs in formal obedience training classes. More than 20% of these dog owners, the study also showed, participate in dog shows. Thus, it is obvious that people who train their dogs are more likely to participate in dog shows than are people who do not train their dogs.
The conclusion above is correct provided which of the following statements is also true?
a) It is impossible for a dog to compete in a dog show if the dog has not completed at least one formal obedience training class.
b) The proportion of dog owners who enroll their dogs in formal obedience training classes in representative of the proportion who train their dogs outside such classes.
c) Dog owners who participate in dog shows only train their dogs by enrolling them in formal obedience training lessons.
d) Participation in dog shows is a reliable indicator of how much attention a dog owner pays to his dog.
e) Only purebred dogs can participate in dog shows, so many owners who enroll tehir dogs in formal obedience training classes are excluded from this activity.