Pick up the correct statement from the following:

ANS:D - All the above.

All the above. Here's a brief explanation of each statement:

1. Isotropic consolidation of clay can be obtained in the triaxial apparatus under equal all-round pressure: This statement is correct. Isotropic consolidation refers to consolidation under equal stress in all directions. In a triaxial apparatus, if equal all-round pressure is applied, it can lead to isotropic consolidation of clay.
2. If the present effective stress is the maximum to which the clay has ever been subjected, it is called normally consolidated clay: This statement is correct. Normally consolidated clay refers to clay for which the present effective stress is the maximum stress it has experienced in its history.
3. If the present effective stress in the past was more than the present effective stress, it is called over-consolidated clay: This statement is correct. Over-consolidated clay refers to clay that has experienced higher effective stresses in the past than the present effective stress it is currently experiencing.