A Mother Questions the Decreased Effectiveness of Methylphenidate (Ritalin),prescribed for Her

A mother questions the decreased effectiveness of methylphenidate (Ritalin) ,prescribed for her child's attention deficit-hyperactivity disorder (ADHD) .Which nursing reply best addresses the mother's concern?

A) "The physician will probably switch from Ritalin to a central nervous system stimulant."
B) "The physician may prescribe an antihistamine with the Ritalin to improve effectiveness."
C) "Your child has probably developed a tolerance to Ritalin and may need a higher dosage."
D) "Your child has developed sensitivity to Ritalin and may be exhibiting an allergy."