bān / huì / kāi / shǐ / qián / bān / zhǔ / rèn / ràng / dà / jiā / bǎ / shǒu / jī / tiáo / chéng / jìng / yīn

班会开始前，班主任让大家把手机调成静音。

Before the class meeting began, the homeroom teacher asked everyone to put their phones on silent.