In superficial expansion of solidsA. Increase in thickness is negligible as compared to increase in length and breadthB. Increase in length and breadth is negligible as compared to increase in thicknessC. Both (A) and (B)D. None of the above

The correct option in the case of superficial expansion of solids is:

A. Increase in thickness is negligible as compared to increase in length and breadth.

In superficial expansion, which is also known as area expansion, the increase in thickness is usually much smaller or negligible compared to the increase in length and breadth. This phenomenon is observed in thin objects or surfaces, such as sheets, plates, or membranes, where expansion occurs primarily in the two-dimensional plane rather than in the third dimension (thickness).

Therefore, option A is the correct choice.