Question

why are sex - linked disorders more common in males?
sex - linked disorders are dominant.
sex - linked disorders are more common in females.
males only need to inherit one copy of the allele on a sex chromosome for it to appear.

Explanation:

Sex - linked disorders are often recessive. Males have one X and one Y chromosome. If a recessive allele is on the X chromosome (the most common case for sex - linked disorders), since males don't have a second X chromosome to potentially have a dominant normal allele, they only need to inherit one copy of the recessive allele on the X chromosome for the disorder to appear. Females have two X chromosomes. They would need to inherit two copies of the recessive allele (one from each parent) to show the disorder.

Answer:

Males only need to inherit one copy of the allele on a sex chromosome for it to appear.