Question

which statement is always true when describing sex - linked inheritance?
it results in a dominant trait.
the alleles are found on the x or y chromosome.
the resulting trait is influenced by multiple alleles.
it is affected by alleles on at least three different chromosomes.

Explanation:

Sex - linked inheritance specifically refers to the inheritance of genes located on the sex chromosomes (X or Y). A trait being dominant or recessive is not inherent to sex - linked inheritance. Traits influenced by multiple alleles (like blood type in some cases) is a different concept from sex - linked inheritance. And sex - linked inheritance is about alleles on sex chromosomes (not three different chromosomes).

Answer:

The alleles are found on the X or Y chromosome.