The correct answer is: C. Vertical D.P.C. is not provided in internal walls.
A damp-proof course (DPC) is a barrier that is used to prevent water from penetrating a building’s structure. It is typically made of a material that is impermeable to water, such as bitumen, plastic, or cement.
Horizontal DPCs are typically installed at the base of a building’s walls, while vertical DPCs are installed at the sides of walls. Both types of DPCs are important for preventing water from entering a building and causing damage.
In internal walls, there is no need for a vertical DPC because the water will not be able to penetrate the wall from the outside. The only way for water to enter an internal wall is through leaks in the plumbing or from condensation. These leaks can be easily fixed, so there is no need to install a vertical DPC.
Horizontal DPCs are still necessary in internal walls, however, because they can prevent water from rising up through the ground. This is especially important in areas with high water tables or where there is a risk of flooding.
In conclusion, the correct answer is C. Vertical D.P.C. is not provided in internal walls.