The correct answer is: A. Engels curve
An Engels curve is a graph that shows the relationship between income and the amount of a good or service that a consumer will purchase. It is named after Ernst Engel, a German statistician who first studied the relationship between income and consumption in the 1850s.
Engels curves are typically downward-sloping, which means that as income increases, consumers tend to spend a smaller proportion of their income on a particular good or service. This is because as income increases, consumers have more money to spend on a variety of goods and services, so they are less likely to spend a large proportion of their income on any one good or service.
Engels curves can be used to analyze the consumption patterns of different groups of people. For example, an Engels curve for food would show how much food a person consumes at different levels of income. This information can be used to track changes in the standard of living over time, or to compare the consumption patterns of different groups of people, such as the rich and the poor.
Engels curves can also be used to predict how consumers will respond to changes in prices or income. For example, if the price of food goes up, consumers will likely buy less food. This can be seen by the shift in the Engels curve to the left. Conversely, if income goes up, consumers will likely buy more food. This can be seen by the shift in the Engels curve to the right.
Engels curves are a useful tool for understanding consumer behavior. They can be used to track changes in the standard of living, to compare the consumption patterns of different groups of people, and to predict how consumers will respond to changes in prices or income.
The other options are incorrect because:
- A production indifference curve is a curve that shows all the combinations of inputs that can produce the same level of output.
- A budget line is a line that shows all the combinations of goods and services that a consumer can afford with a given income and prices.
- A ridge line is a line that separates the feasible region from the infeasible region in a linear programming problem.