Hello there!
"American society marry because the couple romantically love each other.
Other society marry for economic purposes. Still other society marry to retain the pureness of the lineage, to secure the family wealth within its grasp, and to further amass power and privileges."
The text is exploring different societies' reasons for marriage and how they feel about it; therefore, the main idea in the above paragraph is D.) Different Societies have different ideas about the purpose of marriage.
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