Among the options given, the genetic disease that is sex-linked is "Royal haemophilia." Hemophilia is a genetic disorder that affects the blood`s ability to clot properly, leading to prolonged bleeding or spontaneous bleeding. It is an X-linked recessive disorder, which means it is more commonly found in males. Since the gene for hemophilia is located on the X chromosome, males who inherit the affected X chromosome will develop the disease, while females typically inherit one normal X chromosome, providing some protection against the disorder. Therefore, the correct answer is "Royal haemophilia."