Respuesta :
C- formed by a stalactite and a stalagmite
A column is formed when a stalactite and stalagmite grow together. The stalactite grows down from the ceiling while the stalagmite grows up from the ground. Stalactites and stalagmites grow in opposite directions, but they are not opposite of columns. A column is not only formed by a stalactite and stalagmite meeting. They can also be formed when a stalactite reaches the ground.