Answer:
C. It includes humor and mistaken identities, but also suffering and
loss.
Step-by-step explanation:
The reason The Tempest is hard to classify as a tragedy, romance, comedy or one of those easy buckets is that it includes themes from many genres. There is fantastical magic, but there are also murder plots. Therein lies the difficulty of classifying it, and the utter genius of Shakespeare.
All the other answer choices are wrong because these reasons wouldn't produce a difficulty in classification, even if they were correct.