Answer:
D. Breathe deeply to help himself stay calm and think clearly.
Step-by-step explanation:
Symptoms of anxiety often include uncontrollable thoughts of very intense but also very unreal and exaggerated worst case scenarios. Ignoring them is unlikely to work since if you could, you would not be experiencing a state of anxiety. Sitting with a rigid posture to stay alert also won't work, as again theses are uncontrollable and take up most of your attention and being alert might just make you experience a full on panic attack. Avoid eating breakfast to avoid nausea also won't work, nausea is a symptom of anxious states but it's not produced by the eating itself, but by the anxiety. Also being hungry might make it harder to focus once the anxiety has passed. Breathing deeply is the best option, as it will slow down your heartbeat and overall the speed of thoughts.