The correct answer is: D. All of these
Vertical construction joints are provided where the shearing forces are minimum in the case of slabs, beams, and girders. This is because the shearing forces are the forces that tend to cause the structure to shear or tear apart. When the shearing forces are minimum, the structure is less likely to fail.
Slabs are horizontal structural elements that support loads from above and transfer them to the supporting members below. Beams are horizontal structural elements that support loads from above and transfer them to the columns below. Girders are horizontal structural elements that support loads from above and transfer them to the foundations below.
All of these structural elements are subject to shearing forces. The shearing forces are greatest at the ends of the elements and decrease towards the center. This is why vertical construction joints are typically located at the ends of the elements.
Vertical construction joints are used to reduce the shearing forces on the structure. The joints are typically filled with a sealant or grout to prevent the flow of water and other fluids. The joints are also typically designed to allow for movement of the structure due to changes in temperature and humidity.