Why is the need for a dry surface prior to developer application more of a disadvantage with a dry developer than with a non-aqueous wet developer?

Because the dry developer only forms a thin film on the surface of the test piece.

Because the solvent in a non-aqueous wet developer penetrates deeper into discontinuities to contact entrapped penetrant and draw it back out.

Because the warm test piece causes evaporation of the solvent in the non-aqueous developer.

All of the above.

None of the above.