Question

how are the alleles for sex - linked traits inherited?
they are passed from the y chromosome in parents to the x chromosome in offspring.
they are passed from the x chromosome in parents to the xy chromosome in offspring.
they are passed from parents to offspring on the x and y chromosomes.
they are passed from any chromosome in the parents to the x or y chromosome in the offspring.

Explanation:

Sex - linked traits are determined by genes located on the sex chromosomes (X and Y). Alleles for these traits are passed from parents to offspring on these sex chromosomes.

Answer:

They are passed from parents to offspring on the X and Y chromosomes.