Lì / shǐ / kè / shàng / lǎo / shī / jiè / shào / le / Xī / Wèi / yǔ / Dōng / Wèi / de / xíng / chéng / guò / chéng

历史课上，老师介绍了西魏与东魏的形成过程。

In history class, the teacher explained how Western Wei and Eastern Wei were formed.