The wild type of a species represents the characteristics that prevail among individuals in natural conditions. for dogs, the wild type has a short body, upward-pointing ears, and a curly tail. even though dachshunds are descended from the wild-type dog, they have long bodies, downward-pointing ears, and a straight tail. which of these best explains how the shape of the dachshund came into being? humans bred various dogs over many generations to select for the dachshund's shape. humans created a gene for the dachshund shape, which they inserted into the dna of a wild-type dog. natural selection led to the shape of the dachshund over many generations. the unique shape of the dachshund spontaneously appeared during a single generation.

The correct answer is A) Humans bred various dogs over many generations to select for the dachshund's shape.

Indeed, wild dogs were bred, recently in time, to select certain characteristics (mostly physical aspects like ears, tails, etc) that were defined "prettier".
For example, at a certain point, a wild dog was born with a straight tail. This dog was interbred with another straight tail dog, as to pass this characteristic to their herds, and so on until today's shape.

Option B is not true because breeds were created far before the genetic manipulations and DNA were discovered.

Option C is not true because the natural selection actually brought to wild-type dogs, an evolution of wolves.

Option D is not true because not the whole shape of the dachshund appeared spontaneously, but just one characteristic that was progressively selected by humans.