The egg cells of a dog have 39 chromosomes, which are haploid (half the number of chromosomes). In dogs, like in many other mammals, body cells are diploid, meaning they have two sets of chromosomes.
Therefore, if the egg cells have 39 chromosomes, the body cells will have: 39 chromosomes (from the egg) × 2 = 78 chromosomes.
The answer is C. 78.