A 5-year-old boy presents with a waddling gait, increased lumbar lordosis, and difficulty in assuming an erect position. His maternal uncle has Duchenne Muscular Dystrophy (DMD).Which of the following is most likely to be correct?

A、 His mother is unlikely to be a carrier
B、 His sister certainly carries the gene
C、His is more likely than not to have a detectable deletion or duplication in his dystrophin gene
D、 Muscle biopsy is essential to confirm the diagnosis
E、He will have been symptomatic since birth with greatly delayed gross motor skills