Answer:
C. The people felt relief at the end of their journey.
Step-by-step explanation:
In this context, the sentence in quotation marks means that the people who had just endured a long and dangerous trip across the ocean felt relieved that their travels were over and that they were able to stand on solid ground once again. The sentence is, indeed, a simile, in which something, stepping foot on solid ground, is likened to something else, in this case, breathing fresh air.