In order to figure out the correct identification for Y, it is useful to recognize X as an ancient volcanic neck that has been exposed over time due to weathering and erosion.

Therefore, knowing that Y is connected to X and is of similar appearance, it would make sense that Y is also a feature of intrusive volcanic origin. Therefore, a rift [A] (an opening in the earth's crust made by splitting) and an esker [D](a long snake-like formation consisting of sands and gravels left by a glacial stream) are not logical choices. So that leaves either a sill [B] or a dike [C]. Both are intrusive volcanic features and at first glance, Y appears to be horizontal in appearance so one would say sill. However, the fact that is exposed so close to the surface would give more credence to selecting a dike as it is a vertical wall extending upwards from below.