孩子们喜欢在小石子路上跑来跑去。

The kids love running on the path covered with ___gravel.

工人们用碎石铺停车场以增加摩擦力。

The workers ___gravelled the parking lot for better traction.

这个数学问题完全把我难住了。

This math problem totally ___stumped me.