Correct Option: B Explanation of Why Option B is Correct: The concept of "optimum population" refers to the ideal number of people that can be supported by a given set of resources in a country, maximizing the overall welfare and productivity of the population.

1. Productive Effort Per Man: Option B states that the optimum population is reached when "the productive effort per man is at its highest with a given volume of resources." This means that when the population is at its optimum level, each individual can contribute maximally to the economy without overexploiting resources.
2. Resource Utilization: At this point, resources are utilized efficiently. If the population is too low, there may be underutilization of resources, leading to lower overall productivity. Conversely, if the population is too high, it can lead to overpopulation, where resources become strained, and productivity per person decreases due to factors like overcrowding, depletion of resources, and increased competition for jobs.
3. Economic Efficiency: The optimum population ensures that the economy operates at its most efficient level, where the marginal product of labor is maximized. This means that each additional worker adds a significant amount to total output, and the economy can sustain this without diminishing returns.

Why the Other Options Are Wrong or Weaker:

• Option A: All factors of production have been fully employed While full employment of factors of production is important, it does not necessarily indicate that the population is at its optimum level. A country can have all factors of production employed but still be overpopulated or underpopulated. For example, if a country has a high population but limited resources, not all individuals may be effectively contributing to production, leading to inefficiencies.
• Option C: The total population of a country increases This option is misleading. An increase in total population does not automatically mean that the optimum population has been reached. In fact, a growing population can lead to overpopulation, where the number of people exceeds the resources available, resulting in lower productivity per person and potential economic decline.
• Option D: The natural resources of a country increases While an increase in natural resources can support a larger population, it does not define the optimum population. The optimum population is more about the balance between the population size and the available resources rather than just the quantity of resources. Simply having more resources does not guarantee that the population is at its optimum level.

Summary of Key Points:

• The optimum population is achieved when productivity per person is maximized with existing resources.
• Efficient resource utilization is crucial for maintaining high productivity levels.
• Overpopulation or underpopulation can lead to inefficiencies in the economy.
• The optimum population is not solely determined by the total population size or the amount of natural resources available.

This understanding of optimum population is essential for analyzing economic policies and planning for sustainable development.