The correct answer is D. Positive.
Income elasticity of demand measures the responsiveness of the quantity demanded of a good to a change in income. It is calculated as the percentage change in the quantity demanded divided by the percentage change in income.
Normal goods are goods whose demand increases when income increases. This is because consumers have more money to spend on goods and services when their income increases. As a result, the income elasticity of demand for normal goods is positive.
Inferior goods are goods whose demand decreases when income increases. This is because consumers have more money to spend on goods and services that they consider to be of higher quality when their income increases. As a result, the income elasticity of demand for inferior goods is negative.
For necessities, the income elasticity of demand is close to zero. This is because consumers will continue to buy necessities even when their income decreases.
For luxuries, the income elasticity of demand is greater than 1. This is because consumers will buy more luxuries when their income increases.