Final answer:
The atypical symptom of ADHD from the given options is superintelligence, as the characteristic symptoms are inattention, hyperactivity, and impulsivity (option d).
Step-by-step explanation:
The symptom that is not a typical symptom of attention deficit/hyperactivity disorder (ADHD) is d) Superintelligence. The typical symptoms of ADHD include a) Inattention, which is characterized by a lack of focus, b) Hyperactivity, which refers to a higher level of activity than is normal for the individual's age and development, and c) Impulsivity, which involves acting without thinking about the consequences. Superintelligence is not associated with ADHD.
Hence, the answer is option d.