Which of the following characteristics defines attention deficit hyperactivity disorder (ADHD)?

The defining characteristic of attention deficit hyperactivity disorder (ADHD) is indeed unusual inattentiveness or hyperactivity. Individuals with ADHD often struggle to maintain focus on tasks and may exhibit excessive levels of activity that are not appropriate for the situation. This can manifest as difficulty staying on task, forgetfulness, or difficulty organizing activities. The hyperactivity component can include fidgeting, excessive talking, or an inability to remain seated when expected, highlighting the challenge in self-regulation often faced by those with this condition.

In contrast, a preference for sedentary activities indicates a more passive behavior, which does not align with the symptoms of ADHD, where active engagement or impulsiveness is commonly observed. Similarly, consistent focus on tasks and having a stable mood without impulsivity are characteristics that typically do not apply to individuals with ADHD, as the condition inherently involves challenges in maintaining attention and managing impulses. Therefore, option B accurately captures the essence of ADHD symptoms.