GMAT Sentence Correction (SC) | Stalactites and stalagmites, accretions of minerals formed

Stalactites and stalagmites, accretions of minerals formed over time by dripping water, are common features in the region’s corners.

A. formed over time by dripping water, are common
B. that are formed by water dripping over time, are common
C. formed through time by the dripping of water, are common
D. having formed over time through dripping water, is a
E. , which are formed over time by the dripping of water, are commonly