The correct answer is: A. Dead load only
Dead load is the weight of the structure itself, including the weight of the materials used to build it. Live load is the weight of people, furniture, and other objects that will be using the structure.
Differential settlement is the uneven sinking of a foundation. It can be caused by a number of factors, including the type of soil, the weight of the structure, and the presence of water.
To minimize the effect of differential settlement, the area of a footing should be designed for the dead load only. This will ensure that the footing is strong enough to support the weight of the structure without sinking unevenly.
The other options are incorrect because they include live load. Live load is a variable load, which means that it can change over time. This makes it difficult to design a footing for live load, as the exact amount of live load that will be applied to the structure is unknown.
In addition, live load is typically much less than dead load. This means that designing a footing for live load would result in an unnecessarily large and expensive footing.