zài / lì shǐ kè shàng / lǎo shī / jiè shào le / Shǎn Gān Níng Biān qū / de / jiàn shè / chéng jiù

在历史课上，老师介绍了陕甘宁边区的建设成就。

In history class, the teacher introduced the achievements in the development of the Shaanxi-Gansu-Ningxia Border Region.