孩子们在操场上进行自由活动，没有任何规则限制。

The children engaged in ___free-form play on the playground without any rules.

孩子们在艺术课上可以自由发挥，用各种颜料进行创作。

The children enjoyed ___free-form painting with all kinds of colors in art class.

这个课程采用自由形式的教学方式，让学生自己选择研究课题。

The course uses a ___free-form approach where students choose their own research topics.