xiào / zhǎng / yī / xuān / bù / huó / dòng / kāi / shǐ / xué / shēng / men / jiù / yī / hū / bǎi / yìng / fēn / fēn / bào / míng / cān / jiā

校长一宣布活动开始，学生们就一呼百应，纷纷报名参加。

As soon as the principal announced the start of the event, the students responded enthusiastically and signed up.