Question

this is caused by the inability of the body to make dystrophin (a muscle protein). this causes the muscles to become weak as the person ages. this disease primarily affects boys. signs and symptoms typically present before the age of six and may include a delay of motor milestones and progressive weakness in the lower extremities and pelvis. since all muscles are affected, the person will eventually require a wheelchair and assistance with breathing
a oa
b cp
c dmd
d ra

Explanation:

Duchenne muscular dystrophy (DMD) is an X - linked recessive disorder. The gene for dystrophin is located on the X chromosome. Males have one X and one Y chromosome. If the X chromosome has a mutation in the dystrophin - encoding gene, they will develop DMD as they have no normal allele to compensate. Females have two X chromosomes, so they are less likely to be affected (unless they have a very rare situation like inheriting two mutant alleles). Symptoms start early (before age 6), with muscle weakness. Dystrophin is crucial for muscle structure and function. As the disease progresses, muscle weakness worsens, leading to wheelchair use and respiratory issues.
Osteoarthritis (OA) is a degenerative joint disease, not related to dystrophin deficiency. Cerebral palsy (CP) is due to brain damage, not a muscle - protein - related genetic defect. Rheumatoid arthritis (RA) is an autoimmune disease affecting joints, not caused by lack of dystrophin.

Answer:

C. DMD