The efficiency of a plant is of least concern when it is selected as

peak load plant
casual run plant
either (A) or (B)
base load plant

The correct answer is: A. peak load plant

A peak load plant is a type of power plant that is used to meet the peak demand for electricity. Peak demand occurs during times of high usage, such as in the morning and evening when people are at home using electricity for things like cooking, laundry, and watching TV. Peak load plants are typically not very efficient, but they are important because they can provide the extra power that is needed during peak demand times.

A casual run plant is a type of power plant that is used to meet the demand for electricity when other plants are not available. Casual run plants are typically not very efficient, but they are important because they can provide power when it is needed.

A base load plant is a type of power plant that is used to meet the base demand for electricity. Base demand is the minimum amount of electricity that is used at all times. Base load plants are typically very efficient, because they need to be able to operate 24 hours a day, 7 days a week.

Therefore, the efficiency of a plant is of least concern when it is selected as a peak load plant.