Answer:
A. The story starts on the day of Gregor's birth and is told in flash-forwards until the day that Gregor transforms into a bug.
B. The story starts on the day of Gregor's transformation and is told in flashback from various characters' points of view.
C. The story starts on the day of Gregor's transformation and backward to reveal how the events came about.
D. The story starts on the day of Gregor's transformation and continues forward in chronological order.