Because Elsa has received a confirmed diagnosis of beta-thalassemia major, which of the following statements is true about her parents? a. Only her mother carried the gene that caused her blood disorder.
b. Only her father carried the gene that caused her blood disorder.
c. If her parents have another child naturally, there is a 100% chance that the second child will be diagnosed with beta-thalassemia major.
d. If her parents have another child naturally, there is a 25% chance that the second child will be diagnosed with beta-thalassemia major.