The correct answer is A. Plant reserve capacity will be zero.
The plant reserve capacity is the amount of power that a power plant can generate in excess of its maximum demand. If the maximum demand on the plant is equal to the plant capacity, then there is no need for any reserve capacity, and the plant reserve capacity will be zero.
The diversity factor is a measure of how much the demand on a power plant varies over time. A diversity factor of unity means that the demand is constant, while a diversity factor of less than unity means that the demand varies. A lower diversity factor indicates that the demand is more variable, and therefore requires more reserve capacity.
The load factor is a measure of how efficiently a power plant is being used. A load factor of unity means that the plant is being used at its full capacity all the time, while a load factor of less than unity means that the plant is not being used at its full capacity. A lower load factor indicates that the plant is being underutilized, and therefore could be more efficient if it were used more often.
In the case where the maximum demand on the plant is equal to the plant capacity, the diversity factor and load factor are both irrelevant. The only thing that matters is the plant reserve capacity, which will be zero.