The only genotype that would lead to a spotted phenotype in this dog breed, given that the allele B for a black coat is dominant and the allele b for a spotted coat is recessive, is bb. The presence of at least one dominant allele (B or Bb) would result in a black coat, while only the homozygous recessive genotype (bb) would result in the spotted phenotype.
So, the correct response is: bb.