Final answer:
Generalized Anxiety Disorder (GAD) is the correct answer. It is characterized by excessive worrying, difficulty concentrating, irritability, and sleeping problems.
Step-by-step explanation:
The correct answer is Generalized Anxiety Disorder (GAD). GAD is characterized by excessive worrying that is difficult to control and is not specific to any particular situation or event. It is associated with physical symptoms such as difficulty concentrating, irritability, and sleeping problems. People with GAD often experience anxiety that seems to have no real source, which sets it apart from other anxiety disorders like panic disorder, obsessive-compulsive disorder, phobia, and agoraphobia.