I believe the answer might be c, but I can't say for certain since it's been a long time since I read the book.
Answer:
The natural phenomenon of cultural practices among people
Explanation:
Response:
Dependent/subordinate clause
Clarification:
Dependent or subordinate clauses cannot stand alone and need to be linked to an independent clause to have meaning. Moreover, they typically start with a subordinate conjunction, such as since, because, after and even though.
The alternative choices are incorrect because main and independent clauses convey a complete idea, and there is no gerund present to create a gerund phrase.
