It wasn't a test day, there were no oral reports due, and the class was getting ready to view a video. Regardless of the relaxed nature of the class, Baxter suddenly felt his muscles tighten and his heart rate increase as if he had a sudden fright. It was happening again. These symptoms are typical of:

a. a panic disorder.

b. a phobia.

c. a generalized anxiety disorder.

d. an obsession.

I think it is a but then I thought c or d might be right.

It's D

It's D, handed in my test and that was my result

The word sudden & fright removes the possibility of GAD which is a general thing present always. It should be a phobia e.g. claustrauphobia I.e. fear of closed space. Panic disorder happens when there is an immediate stressor in form of a task like a test or assignment.

Hence it is phobia.

There was nothing to cause the "attack", it came out of no where which is what makes me think it was a panic disorder aka panic attack

It's D, Obsession. That is 100% correct.

It is D. Why are so many people answering to this now? This was in 2011!

I agree with c.