ANS:E - All the above.

1. The property of a soil that enables it to become stiff in a relatively short time on standing is called thixotropy: Thixotropy refers to the property of certain substances, such as clays, to become less viscous and more fluid when agitated or stressed and to return to a more solid state when left to stand. Therefore, this statement is incorrect as it does not accurately define thixotropy in the context of soil mechanics.
2. The ratio of shear strength in the natural state to the remolded shear strength under undrained conditions, is called the degree of sensitivity: This statement is correct. The degree of sensitivity is indeed defined as the ratio of the undrained shear strength of a soil in its natural state to the undrained shear strength of the same soil after remolding.
3. The difference between the undisturbed shear strength and remolded shear strength is known as remolding loss: This statement is also correct. Remolding loss refers to the reduction in shear strength that occurs when a soil is remolded or disturbed from its natural state.
4. The tendency of dense sand to expand on the application of a shearing load is known as dilatancy: This statement is correct. Dilatancy refers to the phenomenon where dense soils, such as sands, tend to increase in volume or expand when subjected to shearing stresses.