A 23-year-old woman comes to the physician for genetic counseling prior to conception. Her brother and maternal uncle had Duchenne mcular dystrophy (DMD) and died at the ages of 28 and 17 years, respectively. Genetic analysis was not performed on either relative prior to death. Serum studies show a mcle creatine kinase concentration of 120 U/L (N=22– 198). The patient's 50-year-old mother has a serum mcle creatine kinase concentration of 300 U/L. Which of the following is the most appropriate assessment of this patient's carrier stat for this disease? (A) The patient has a 50% risk for developing DMD (B) The patient has a 50% risk of having a child with DMD (C) The patient is a carrier of the disease based on her family history of DMD (D) The patient is not a carrier of the DMD based on her normal creatine kinase concentration (E) The patient's DMD carrier stat is uncertain becae of random X inactivation