an important event in the author’s life
Option C.
Step-by-step explanation:
The passage given in the question has been taken from "Ellis island" which has been written by Barbara Davis Pyle. It is about an important event in the life of the author which speaks about when the author along with his parents crossed the harbor of city and entered the United States of America.
This was the event of starting a new life by the author with his family. This it was one of the major and happy events.