The modern domesticated dog is thought to be descended from the wild wolf. There are currently many breeds of domesticated dogs that vary greatly in appearance. Which of the following best describes how the modern-day dog has changed from its ancestor, the wolf? Humans have cloned dogs for desirable traits, causing many differences among breeds. B Humans have bred dogs for desirable traits, causing many differences among breeds. C The modern dog gradually changed over time due to natural selection. D The modern dog quickly changed due to extinction.