那个孩子跑步时跌倒了，擦伤了膝盖。

The child ___tumbles while running and scrapes his knee.

石油价格因全球需求下降而暴跌。

Oil prices ___tumbled due to a drop in global demand.

孩子们在草地上快乐地翻跟头。

The children happily ___tumble on the grass.

孩子们欢笑着滚下草坡。

The children laugh as they ___tumble down the grassy hill.