The correct answer is: B. law of diminishing return as applied to agriculture
The Malthusian theory of population is based on the idea that population growth will always tend to outstrip the growth of food production, leading to poverty and starvation. This theory is based on the law of diminishing returns, which states that as more and more resources are used to produce a good, the marginal return (the additional output obtained from using an additional unit of input) will eventually decrease.
In the context of agriculture, this means that as more and more land is used to grow crops, the amount of food produced per unit of land will eventually decrease. This is because as more land is used, the land that is left will be less fertile and will require more inputs (such as fertilizer and water) to produce the same amount of food.
The Malthusian theory of population has been criticized for being too simplistic and for not taking into account factors such as technological innovation and economic development. However, it remains a powerful tool for understanding the relationship between population growth and economic development.
The other options are incorrect because:
- Option A is based on the law of demand, which states that, all other things being equal, the quantity demanded of a good will decrease as the price of the good increases. This law does not apply to population growth, which is not determined by the price of food.
- Option C is based on the law of marginal utility, which states that the marginal utility of a good decreases as the consumer consumes more of the good. This law does not apply to population growth, which is not determined by the marginal utility of food.
- Option D is based on the law of marginal return, which states that the marginal return to a factor of production decreases as more of the factor is used. This law does apply to agriculture, but it is not the basis of the Malthusian theory of population.