This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Attention deficit hyperactivity disorder is seen in 
Select and explain. 
A. Insulin resistance, B. Thyroid hormone resistance, C. Testosterone deficiency, D. Calmodulin Deficiency
D: Calmodulin Deficiency
Answer: D: Calmodulin Deficiency 
Explanation: ADHD:

Attention Deficit Hyperactivity Disorder.
Difficulty in paying attention, difficulty in controlling behavior and hyperactivity.
Etiology- both genetic and environmental factors. Abnormality in dopamine transporter and thyroid receptor beta genes in some patients.

Three subtypes are known:

Predominantly hyperactive-impulsive
Predominantly inattentive
Combined hyperactive-impulsive and inattentive.

Diagnosis is primarily clinical, using thorough clinical interview of parents and use of behavior rating scales. Physical examination includes direct observation of the child and ruling out chronic systemic illnesses that affect child's attention span.