这座磨坊已经碾磨谷物上百年了。

This ___mill has been grinding grain for over a hundred years.

这家造纸厂每天生产大量纸张。

The paper ___mills produce tons of paper every day.

游客们无所事事地在广场上闲逛。

The tourists were ___milling around the square with nothing to do.