A Dog Breeder Wishes to Develop a Breed That Does

A dog breeder wishes to develop a breed that does not bark.She starts with a diverse mixture of dogs.Generation after generation,she allows only the quietest dogs to breed.After 30 years of work she has a new breed of dog with interesting traits,but on average,the dogs still bark at about the same rate as other dog breeds.Which of the following would be a logical explanation for her failure?

A) There is no variation for the trait (barking) .
B) There was no selection (differential reproductive success) related to barking behavior.
C) The tendency to bark is not a heritable trait.
D) The selection was artificial,not natural,so it did not produce evolutionary change.