Economists refer to the necessity of holding all variables other than price constant in constructing a demand curve as the A. substitution effect. B. income effect. C. law of demand. D. ceteris paribus condition.

D. ceteris paribus condition

Explanation:

The Latin words "Ceteris paribus", means "all other things remain the same". It is an assumption usually included when by economists when stating laws or concepts such as demand and supply. Because, actually in the real word, it is feasible to eliminate other variables that might influence an outcome, aside the variables under study. So therefore, we assume all other variables remain constant, when stating the relationship between two variables. For example, when constructing a demand curve showing the relationship between price and quantity demanded, we assume that all other variables that can influence demand other than price, remain the same, which in reality might be difficult to isolate.