The floor is rubbed with oxalic acid, for making its surface A. Free from voids B. Glossy C. Durable D. Uniform

The correct answer is: B. Glossy.

Oxalic acid is a strong acid that can be used to clean and polish surfaces. When rubbed on a floor, it can remove dirt, grime, and stains, and leave the surface looking shiny and glossy.

The other options are incorrect because:

• A. Free from voids: Oxalic acid is not a substance that can fill in voids in a surface.
• C. Durable: Oxalic acid can make a surface more durable, but it is not the only factor that affects durability.
• D. Uniform: Oxalic acid can make a surface more uniform, but it is not the only factor that affects uniformity.

In conclusion, the floor is rubbed with oxalic acid to make its surface glossy.