monogamy

许多天鹅在繁殖季节保持一夫一妻制。

Many swans practice ___monogamy during the breeding season.

在许多文化中，一夫一妻制是社会的主流婚姻形式。

In many cultures, ___monogamy is the predominant form of marriage.

在现代社会中，一夫一妻制被广泛接受为婚姻的标准形式。

In modern society, ___monogamy is widely accepted as the standard form of marriage.