If a genetic mutation occurs in the phenotype of individual, what must be true for the new phenotype to be inherited by the offspring of the individual?
the mutation must be beneficial.
the mutation must be on a recessive allele.
the mutation must be harmful to the individual.
the mutation must be in a gamete of the individual.

The correct answer is the last statement, that is, the mutation must take place in a gamete of the individual.

Explanation:

For a mutation to be heritable, there is a need for them to take place in the gametes or the germ cells only. In case if the mutations take place in the somatic cells, it does not get transmitted to the next generations.  

The combination of male and female gamete takes place to produce the zygote that in turn establishes into new individuals. Thus, any mutation taking place in the DNA of these gametes will be passed on to the upcoming offspring.  

wadadadwawadwdwdaddwawdwad