Answer:
A mutation in his offspring
Explanation:
A mutation can be described as any change which occurs in the DNA of an organism. Mutations can be either heritable or non-heritable
If a mutation occurs in the gamete cells of a male, the mutation will be heritable and will occur in his offsprings.
Other options, like option D, is not correct because a mutation in the gamete cells will not cause a mutation in the somatic cells. Gamete cells are the sex cells and hence mutation will arise in the sex cells.