Body odor is an X chromosome dominant inheritance
Whether the mother has a son or not, it means that the mother (chromosome XX) is a heterozygous carrier of the gene (one X is carried, and a homozygote is two X carriers) ,
The X on the son's chromosome XY does not carry the body odor gene. As long as the son's wife does not have body odor, 100 of his offspring will not.
But if his wife also has body odor, as long as she is not a homozygote, the probability of the offspring having body odor is only 50%, and if it is a homozygote, it is 100%.