圣海伦斯山是美国的一座活火山。

Mount St. Helens is an ___active volcano in the United States.

科学家们正在监测这座活火山，寻找喷发的迹象。

Scientists are monitoring the ___active volcano for signs of an eruption.

由于该活火山活动增加，当局已发布警告。

Authorities have issued a warning due to increased activity at the ___active volcano.