Steven has the dominant tongue rolling phenotype but he does not know his genotype. his wife has the recessive non-tongue rolling trait. if their son cannot roll his tongue this means

Steven has heterozygous genotype.

Explanation:

Tongue rolling is a dominant trait, that means the trait can express itself at the homozygous dominant and as well as in the heterozygous condition. The recessive homozygous condition is not able to express this trait.

Steven can roll his trait, this means his genotype is either homozygous dominant or heterozygous. The wife is recessive for the trait. Their son cannot roll his tongue, this means the Steven is heterozygous dominant. If the Steven is homozygous dominant his son will be able to express the trait.

Thus, the answer is Steven has heterozygous genotype.

a covalent bond, specfically triple bond