The answer is D: he slowly realizes that he is a bug and starts to feel sad and confused.
As the story progresses in Kafka´s strange and beautiful Metamorphoses, Gregor becomes accustomed to having been transformed into a bug and this brings him to a point of confusion and sadness where he begins to question not only his current state, but his previous life as clerk in some office. He begins to ponder the meaninglessness of his previous life at the same time that he cannot but wonder what meaning he could ever find now that he has become nothing more than a bug and a nuisance to his family.
