Answer: C) Caste system
Explanation:
Caste system is the system in which people is divided into certain groups as per their social rank, status, race and background. This system is followed and assigned by the people belonging to that community.
According to the question,Mira is following the caste system to which she belongs.She is married to the person of same caste .She got involved with people of similar caste hers in her childhood.
Other options are incorrect because class system, slavery, petalism and ostracism is not the system that is based on class of people.Thus, the correct option is option(C).