Parents of a 3-year-old boy noticed that their son was walking "on his toes", had a waddling gait, fell frequently, had difficulty getting up again, and was not able to run because of the difficulty in lifting his knees. at age five, there was progressive muscular weakness and atrophy. weakness of the trunk muscles led to increased lordosis and a protuberant abdomen. he was able to speak clearly and the muscles of his face functioned normally. at age 9, he was confined to a wheelchair. circle the disorder you believe is the cause of the described symptoms. explain your choice, including why the other disorder were eliminated.
a. muscular dystrophy
b. multiple sclerosis
c. myasthenia gravis
d. polio