历史教科书详细记录了20世纪发生的几次大规模种族灭绝事件。

History textbooks document several major ___genocides that occurred in the 20th century.

联合国呼吁国际社会共同行动，防止未来发生种族灭绝。

The UN urges the international community to take joint action to prevent future ___genocides.