工人们把啤酒装进木桶里等待发酵。

The workers filled the ___barrels with beer for fermentation.

枪管需要定期清理以防止堵塞。

The ___barrel of the gun needs regular cleaning to prevent jamming.

这家炼油厂每天能处理十万桶原油。

The refinery can process 100,000 ___barrels of crude oil per day.

摩托车在空旷的公路上飞驰。

The motorcycle was ___barrelling down the open road.