The correct answer is: A. insufficient capacity.
Insufficient capacity is a limiting factor in a plant when the plant is not able to produce enough goods or services to meet the demand. This can be due to a number of factors, such as a lack of workers, machinery, or raw materials.
A shortage of experienced salesmen is not a limiting factor in a plant. Salesmen are responsible for selling the plant’s products or services, but they do not directly affect the plant’s production capacity.
A general shortage of power is not a limiting factor in a plant. Power is an essential input for many plants, but it is not the only input. Plants can also use other sources of energy, such as natural gas or oil.
A shortage of materials is a limiting factor in a plant. Materials are essential inputs for many plants, and if they are not available, the plant will not be able to produce goods or services.
In conclusion, the correct answer is: A. insufficient capacity.