There is a joke, which is composed of Liu Huan's songs. Who can send it?

In geography class, the teacher asked the students: Who knows the direction of the Yellow River? A student sang: The river flows eastward. The teacher ignored him and continued to ask: Who knows the distribution of stars? Students continue to sing: the stars in the sky join Beidou. Teacher: Are you crazy? Student: You have, I have, all of them. Teacher: Get out ~ ~! Student: Let's go, let's go ~ We walked out of the classroom while singing.