Which of the following describes a normal good?

A normal good is characterized by an increase in demand when consumer income rises. This relationship reflects the income elasticity of demand being positive, indicating that as consumers have more income, they have a tendency to purchase more of these goods. Normal goods can further be classified into two categories: necessary goods, which have an income elasticity between zero and one, and luxury goods, which have an income elasticity greater than one. In both cases, the key characteristic is the positive correlation between income and quantity demanded, which aligns perfectly with the correct answer.

The other options describe scenarios that do not fit the definition of normal goods. For instance, a good with negative income elasticity would pertain to inferior goods, which experience a decline in demand as income rises. A good with an income elasticity greater than one is a luxury good, a specific subclass of normal goods, but does not encompass all normal goods. Lastly, a good that decreases in demand as income increases directly contradicts the fundamental principle of normal goods. Thus, the correct answer highlights the essential trait of normal goods in economic theory.