Answer:
c. gregors father throws an apple at him, which lodges in his back
Step-by-step explanation:
The climax in a story is the moment of greatest tension in the plot, where the reader is anxious and ground to advance in the reading to know what will happen. In "Metamorphosis" the climax is at the moment when Gregor's father throws an apple on his back. The apple is stuck on Gregor's back and this creates a lot of tension in the story, as it will trigger unpredictable and important events in the narrative.
"Metamorphosis" was written by Kafka and tells the story of how Gregor Sansa wakes up transformed into a giant insect and has to deal with the loss of humanity, the lack of affection and human contact and the rejection of everyone around him.