Final answer:
Grete justifies that the bug is not actually Gregor by claiming that it is just a bug pretending to be Gregor. She argues that the real Gregor would never have turned into a bug, and that this imposter bug cannot possibly be her brother.
Step-by-step explanation:
Grete justifies that the enormous bug is not actually Gregor by claiming that it is just a bug pretending to be Gregor. She argues that the real Gregor would never have turned into a bug, and that this imposter bug cannot possibly be her brother. Grete points out that the bug behaves differently, it doesn't have the same memories or emotions as Gregor, and it does not exhibit any signs of recognition towards the family. Therefore, she concludes that the bug is not Gregor.