They danced until they were so tired that they fell to the ground, still laughing and gasping for air.

### 解释 gasping 是动词 gasp 的现在分词形式，gasp 的意思是"喘气、喘息"，通常指因为剧烈运动、惊讶或呼吸困难而急促地吸气。gasping 在这里表示"一边笑一边急促地呼吸"的状态。