David is excitable, impulsive, and very active. he also has great difficulty concentrating. he most likely has

Attention-deficit/hyperactivity disorder

Explanation:

From the question, we can see that David is excitable, impulsive, and 'very' active. Another thing to take note from the question is that David has great difficulty concentrating. The high activity of David, the impulsiveness of David and the concentration difficulty of David are the symptoms of Attention-deficit/hyperactivity disorder which is also known as ADHD. Other symptoms of the Attention-deficit/hyperactivity disorder includes depression, mood swings, aggressiveness and so on.

Attention-deficit/hyperactivity can be treated by using Antihypertensive medications and by using a therapy that is based on talking.

permafrost layer, it exists beneath a layer of soil, rock or sediment.

answer; colony;