Reproduction of dogs

Question
Can puppies have more than one dad? And can you just explain your answer to me please.

Answer
Yes. The sperm from one dog may fertilize some eggs of the female; and then if  another male breeds with the female, that dogs sperm may fertilize other eggs, thus resulting in a litter with two different fathers. The American Kennel Club actually has a "multiple-sire" program where they purposely breed this way and then test the puppies to see which puppies were sired by which male.