What geographical feature is described as having openings from which material is ejected?

The correct answer is that the geographical feature described as having openings from which material is ejected is volcanoes. This occurs because volcanoes are geological structures formed by the movement of tectonic plates and the accumulation of magma from the Earth's mantle. When pressure builds up, they can erupt explosively or ooze lava, ejecting ash, gases, and other volcanic materials into the atmosphere or surrounding area. This unique characteristic distinguishes volcanoes from other geographical features.

In contrast, mountains are primarily formed through tectonic forces and do not have openings for material to be ejected. Rivers are flowing bodies of water that transport sediment and nutrients but do not involve ejection of material from openings. Canyons are formed through erosion processes, mainly by water, and also do not have openings for ejection. Understanding these distinctions helps clarify why volcanoes fit the description provided in the question.