Answer:
The answer is the first option: The sea is compared to a boiling pot, emphasizing its churning.
Step-by-step explanation:
The excerpt is comparing vomiting, sea and fire. In this case, the first option is the correct one as "churning" refers to a mixture of something --this context--. Option B is not possible as the depth has nothing to do with vomiting in first instance. The other option are definitely not possible as "heaven" here is only mentioned as a expression, not as the meaning of heaven per se. So basically, heaven here is not being compared whatsoever.