孩子们在操场上无拘无束地奔跑玩耍。

The children played and ran around the playground in an ___unconstrained manner.

在轻松的聚会上，她展现出无拘无束的笑容。

At the casual party, she showed her ___unconstrained smile.

在这个理论模型中，粒子的运动是没有任何限制的。

In this theoretical model, particles exhibit ___unconstrained motion.