lǎo shī / ràng / wǒ men / bǐ jiào / shé jiān hòu yīn / hé / shé jiān qián yīn / zhè / liǎng ge / shēng mǔ / de / fā yīn / chā bié

老师让我们比较舌尖后音和舌尖前音这两个声母的发音差别。

The teacher asked us to compare the pronunciation differences between the retroflex and alveolar initials.