ANS:D - all the above.

1. Expulsion of double-layer water from in between the grains: This is a fundamental aspect of clay behavior known as double-layer compression. Under pressure, water molecules within the double layer surrounding clay particles are forced out, allowing the clay particles to come closer together, thereby causing compression or consolidation of the clay mass.
2. Slipping of particles to new positions of greater density: While some particle rearrangement may occur during compression, the slipping of particles to new positions of greater density is not typically considered a primary mechanism of clay compressibility. Instead, it's the expulsion of water and rearrangement of clay particles that contribute significantly to compressibility.
3. Bending of particles as elastic sheets: Clays are known for their plate-like structure, but the bending of particles as elastic sheets is not a significant factor in clay compressibility. While clay particles may have some degree of flexibility, their compressibility is primarily governed by factors such as water content, soil structure, and interparticle forces.