Question

which combination of alleles are always involved in the inheritance of a sex - linked trait?
○ heterozygous alleles
○ homozygous alleles
○ alleles that are carried on x and y chromosomes
○ alleles that are carried on all chromosomes except the x and y chromosomes

Explanation:

Sex - linked traits are those whose genes are located on the sex chromosomes (X and Y chromosomes). Heterozygous or homozygous alleles are not always the case for sex - linked trait inheritance. Alleles on non - sex chromosomes are for autosomal traits. So the alleles involved in sex - linked trait inheritance are those carried on X and Y chromosomes.

Answer:

alleles that are carried on X and Y chromosomes