Lì / shǐ / kè / shàng / lǎo / shī / jiǎng / jiě / le / mín / shēng / zhǔ / yì / de / zhǔ / yào / nèi / róng

历史课上，老师讲解了民生主义的主要内容。

In history class, the teacher explained the main ideas of the Principle of People's Livelihood.