The correct answer is: A. 25 to 50 mm
The slump test is a measure of the consistency of fresh concrete. It is determined by measuring the amount of slump that occurs when a cone of concrete is filled and then released. The slump test is used to determine the workability of concrete, which is the ease with which it can be placed, compacted, and finished.
The slump of concrete is affected by the water-cement ratio, the type and amount of admixtures, the size and shape of the aggregate, and the temperature of the concrete. The slump of concrete should be specified for the particular project based on the type of concrete, the formwork, and the method of placing and finishing the concrete.
For beams and slabs, a slump of 25 to 50 mm is typically specified. This slump range provides a good balance between workability and strength. A slump that is too low will make it difficult to place and compact the concrete, while a slump that is too high will result in a weak concrete.
The other options are incorrect because they do not fall within the recommended slump range for beams and slabs.