在音乐课上，老师教我们唱‘do、re、mi’这三个音阶。

In music class, the teacher taught us to sing the notes '___do, ___re, ___mi'.

在音乐课上，老师教我们唱音阶：do, ri, mi, fa, sol, la, ti。

In music class, the teacher taught us to sing the scale: do, ___ri, mi, fa, sol, la, ti.