निम्नलिखित में से कौन-सा पारंपरिक रूप से विवाह संस्था का मुख्य समाजशास्त्रीय उद्देश्य या कार्य नहीं है?

The custom or practice in which a man marries the sister of his deceased or living wife is known as:

Exogamy is a rule of marriage which:

Marriage requires both spouses to personally and psychologically adjust to which type of lifestyle?