Genotype question for Biology?

In dogs, there is a hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is either DD or Dd. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be ped on. How can the owner ascertain the exact genotype of the dog? Show Punnett squares to illustrate the possibilities. This type of cross is called a