Answer:
Are you speaking about the actors or the audience? If you are talking about the actors- never! It would be highly irresponsible to fall asleep at your job. If you are talking about the audience- I suppose you can fall asleep whenever, but it would be disrespectful to the actors (unless you are watching the film version).
The correct answers are: B) the dystopian world that Gregor enters as an insect, and C) Gregor's sudden transformation into a giant insect.
A Kafkaesque situation is a nightmarish one, and also strongly surreal, so in that sense, the options that relate the most to said expression are the ones that have to do with dream-like things, like the dystopian world and Gregor becoming an insect.
