question: A 2-year- old boy presents with progressive clumsiness and difficulty walking. On physical examination, the child has
  large calves. He has difficulty walking on his toes and has a waddling gait as shown. Which of the following is the most likely diagnosis?
opa: Becker muscular dystrophy
opb: Myotonic dystrophy
opc: Facioscapulo humeral dystrophy
opd: Duchenne muscular dystrophy