Tamryn Has a Son Who Has Duchenne Muscular Dystrophy,which Is

Tamryn has a son who has Duchenne muscular dystrophy,which is inherited as an X-linked recessive trait.At a molecular level,the disease is due to lack of the protein dystrophin.Tamryn participates in a study that looks at dystrophin levels in various muscles.The study samples cells from 10 different muscles.The study finds that some cells make dystrophin and some do not.An explanation for this finding is that

A) the mutation is only in some muscle cells.
B) Tamryn is making less dystrophin as she gets older.The study should be repeated at different ages.
C) the X chromosome that bears the mutation is turned on in some cells but off in others.
D) Tamryn does not have a Y chromosome.