The correct answer is option 4: underground water.

Stalactite, stalagmite, and pillars are depositional landforms that are formed by the action of underground water. When water seeps through cracks and crevices in rock formations, it carries dissolved minerals with it. As the water drips from the ceiling of a cave, it leaves behind small amounts of these minerals. Over time, these mineral deposits accumulate and form structures called stalactites, which hang from the ceiling.

At the same time, the water that drips to the floor of the cave forms another mineral deposit that grows upwards from the ground. These formations are called stalagmites. Stalactites and stalagmites can eventually meet and form columns or pillars.

It is important to note that while running water, wind, and glaciers also shape the Earth`s surface and create various landforms, they do not directly contribute to the formation of stalactites, stalagmites, and pillars. These unique formations are specifically formed by the slow deposition of minerals carried by underground water.