Samantha began to feel dizzy while she was shopping with her friends. Although the weather was quite cold, she began sweating heavily. Her friends took her to a doctor but he could not identify the reason behind her symptoms. According to the given scenario, which of the following is Samantha most likely suffering from?
a. Huntington's disease.
b. Tay-Sachs disease.
c. Trisomy 21.
d. Panic disorder.