Complex sentence: Marriage in China has undergone change during the country's reform and opening period, especially because of new legal policies like the New Marriage Law of 1980 and the one-child policy introduced in 1979.
Split into simpler sentences: Marriage in China has undergone change during the country's reform and opening period. Much of the change in marriage life can be seen in the relevant legal policies, particularly with the New Marriage Law of 1980 and the one-child policy introduced in 1979.