choochoo

例句：

1. 1. The dog was choo-chooing happily as it ran around the yard.
   狗欢快地在院子里跑着，咕嘟咕嘟地叫着。
2. 2. The milk was choo-chooing in the carton as it sat there.
   牛奶在盒子里咕嘟咕嘟地响着。