ANS:E - 50%

A raft foundation is a type of shallow foundation that covers the entire footprint of a building, distributing the load over a large area of soil to prevent excessive settlement. The size of a raft foundation is typically designed to exceed the plan area of the building by a certain percentage to ensure adequate bearing capacity and to minimize settlement. This additional area allows the foundation to spread the building's load over a larger area of soil, reducing the pressure on the underlying soil and preventing excessive settlement. Among the options provided, the most common design practice is for the area of the raft foundation to exceed the plan area of the building by around 50%. This additional 50% provides a substantial safety factor and ensures that the foundation can adequately distribute the loads from the building to the soil beneath without causing settlement issues. Therefore, the correct answer is: 50%