Lì / shǐ / kè / shàng / lǎo / shī / xiáng / xì / jiǎng / jiě / le / Xī / ān / Shì / biàn / de / bèi / jǐng / hé / yǐng / xiǎng

历史课上，老师详细讲解了西安事变的背景和影响。

In history class, the teacher explained the background and impact of the Xi'an Incident in detail.