The correct answer to the question is:
**O Males because they have only one X chromosome**
Explanation:
1. Sex-linked disorders are genetic conditions that are linked to the sex chromosomes, X and Y. These disorders are more common in males because they have only one X chromosome.
2. In the case of recessive sex-linked disorders, if a male inherits a single recessive gene on his X chromosome, he will exhibit the disorder because he lacks a second X chromosome to mask the effects of the recessive gene.
3. Females, on the other hand, have two X chromosomes. If a female carries a recessive gene for a sex-linked disorder on one X chromosome, the other X chromosome may carry a dominant gene that can mask the effects of the recessive gene, reducing the risk of exhibiting the disorder.
4. Therefore, males are at greater risk for sex-linked disorders due to a recessive gene because they lack a second X chromosome to compensate for the effects of the recessive gene, making the expression of the disorder more likely in males than in females.
